lifornia 

onal 

lity 


UNIVERSITY  OF  CALIFORNIA 
AT  LOS  ANGELES 


GIFT  OF  CAPT.  AND  MRS. 
PAUL  MCBRIDE  PERIGORD 


of 
AT 

LOS  ANGELES 
LIBRARY 


ARTIFICIAL  AND   NATURAL    FLIGHT. 


A  Pockct-Book  of  Aeronautics.— By  H.   W. 

L.  MOEDEBECK.  Translated  from  the  German  by 
Dr.  W.  MANSERGH  VARLEY.  With  150  Illustrations, 
los.  6d.  net. 

CONTENTS. — Gases — Physics  of  the  Atmosphere — Meteoro- 
logical Observations  —  Balloon  Technics  —  Kites  and 
Parachutes  —  On  Ballooning  —  Balloon  Photography  — 
Photographic  Surveying  from  Balloons  —  Military  Bal- 
looning— Animal  Flight — Artificial  Flight  —  Airships — 
Flying  Machines  —  Motors  —  Air  Screws — Appendix  — 
Index. 

"Will  be  highly  welcome  to  all  aeronauts.  It  may  be  said  to  be  the 
only  complete  work  practically  dealing  with  such  matters.  We  have  no 
hesitation  in  thoroughly  recommending  this  as  an  absolutely  indispensable 
book. '" — Knowledge. 

"It  is  without  a  doubt  the  best  book  that  has  appeared  011  the  subject." 
—Aeronautical  Journal. 

"  The  present  volume  ought  certainly  to  be  possessed  by  every  student 
of  Aeronautics,  as  it  contains  a  vast  amount  of  information  of  the  highest 
value."— Glasgow  Herald. 


WHITTAKER    &    CO.,    LONDON,    E.G. 


ARTIFICIAL  AND 
NATURAL    FLIGHT 


SIR    HIRAM    S.    MAXIM. 


WITH     95     ILLUSTRATIONS. 


THE    MACMILLAN    CO., 

64-66    FIFTH    AVENUE,    NEW    YORK. 

WHITTAKER  &  CO.,  LONDON,  E.G. 

1908. 

136510 


TU 


PREFACE. 


IT  was  in  1856  that  I  first  had  my  attention  called  to 
the  subject  of  flying  machines.  My  father,  who  was  a 
profound  thinker  and  a  clever  mechanician,  seems  to  have 
given  the  subject  a  great  deal  of  thought,  and  to  have 
matured  a  plan  identical  with  what  has  been  proposed  by 
hundreds  since  that  time.  I  was  then  sixteen  years  of 
age,  and  a  fairly  good  mechanician,  and  any  new  thing  in 
the  mechanical  line  interested  me  immensely. 

My  father's  proposed  machine,  of  which  he  made  a 
sketch,  was  of  the  Helicoptere  type,  having  two  screws 
both  on  the  same  axis — the  lower  one  to  be  right  hand 
and  mounted  on  a  tubular  shaft,  and  the  top  one  to  be  left 
hand  and  mounted  on  a  solid  shaft  running  through  the 
lower  tubular  shaft.  These  screws  were  to  be  rotated  in 
reverse  directions  by  means  of  a  small  pinion  engaging  a 
bevel  gear  attached  to  each  of  the  shafts.  His  plan  con- 
templated large  screws  with  very  fine  pitch,  and  he 
proposed  to  obtain  horizontal  motion  by  inclining  the  axis 
forward.  He  admitted  that  there  was  no  motor  in 
existence  light  enough,  but  thought  one  might  be  invented, 
and  that  an  engine  might  be  worked  by  a  series  of  ex- 
plosions in  the  cylinder,  that  is,  what  is  known  to-day  as 
internal  combustion ;  but  he  was  not  clear  how  such  an 
engine  could  be  produced.  He,  however,  said  that  a  flying 
machine  would  be  so  valuable  in  time  of  war,  that  it 
mattered  little  how  expensive  the  explosive  might  be, 
even  if  fulminate  of  mercury  had  to  be  used.  It  is 
interesting  to  note  in  this  connection  that  the  great  Peter 
Cooper  of  New  York  thought  out  an  identical  machine 
about  the  same  time,  and  actually  commenced  experiments. 
It  seems  that  this  gentleman  regarded  fulminate  of  mercury 


\L 


vi  PREFACE. 

as  altogether  too  feeble  and  inert,  because  we  find  that 
he  selected  chloride  of  nitrogen  as  his  explosive  agent. 
However,  his  work  was  soon  brought  to  an  end  by  the 
loss  of  the  sight  of  one  eye,  after  which  time  he  had  no 
further  dealings  with  this  lively  explosive. 

The  many  early  conversations  that  I  had  with  my  father 
on  the  subject  kept  the  matter  constantly  before  me,  and 
I  think  it  was  in  1872,  after  having  seen  Roper's  hot-air 
engine  and  Brayton's  petroleum  engine,  that  I  took  the 
matter  up,  and  commenced  to  make  drawings  of  a  machine 
of  the  Helicoptere  type,  but  instead  of  having  one  screw 
above  the  other,  I  saw  at  once  that  it  would  be  much 
better  if  the  two  screws  were  widely  separated,  so  that 
each  would  engage  new  air,  the  inertia  of  which  had  not 
been  disturbed.  The  designing  of  the  machine  itself  was 
a  simple  matter,  but  the  engine  gave  me  trouble.  No 
matter  from  what  point  I  examined  the  subject,  the  engine 
was  always  too  heavy.  It  appears  that  the  Brayton  engine 
was  shown  at  the  Centennial  Exhibition  at  Philadelphia 
in  1876,  and  that  Otto  visited  this  exhibition.  Up  to  that 
time,  he  had  been  making  a  species  of  rocket  engine — that  is, 
an  engine  in  which  an  explosive  mixture  shot  the  piston 
upward  and  then  sucked  it  back,  a  rack  and  pinion 
transmitting  movement  to  the  rotating  shaft  by  means  of  a 
pawl  and  ratchet.  He  appears  to  have  been  much  interested 
in  the  Brayton  engine,  as  it  was  evidently  very  much 
in  advance  of  his  own.  It  actually  developed,  even  at  that 
time,  one  horse-power  per  hour  for  every  pound  of  crude 
petroleum  consumed,  but  it  was  very  heavy  indeed,  very 
difficult  to  start,  arid  not  always  reliable.  The  shaft  that 
worked  the  valve  gear  was  parallel  to  the  cylinder,  and 
placed  in  the  exact  position  occupied  by  a  similar  shaft  in 
the  present  Otto  engine,  but  instead  of  revolving  only 
half  as  fast  as  the  crank  shaft,  it  made  the  same  number  of 
revolutions.  On  Otto's  return  to  Germany,  he  evidently 
profited  by  what  he  had  seen,  and  made  a  new  engine, 
which  in  reality  was  a  cross  between  his  own  and  the 


PREFACE.  vii 

Brayton  ;  the  result  was  a  very  important  invention,  which 
has  been  of  incalculable  value  to  mankind.  It  is  this 
engine  which  is  now  propelling  our  motor  cars,  and  it 
is  the  only  engine  suitable  for  employment  on  a  flying 
machine;  but  even  this  motor  was  not  in  a  sufficiently 
high  state  of  development  as  far  as  lightness  was  concerned, 
to  be  of  any  use  to  me.  The  drawings  which  I  made  in 
1873,  although  of  little  or  no  value,  kept  my  thoughts  on 
artificial  flight,  and  while  I  was  away  from  home  attending 
to  business,  especially  when  in  foreign  countries,  I  often 
amused  myself  by  making  mathematical  calculations. 
Quite  true,  the  formula  which  I  used  at  the  time — 
Has  well's — was  not  correct ;  still,  it  was  near  enough 
to  the  mark  to  be  of  considerable  value.  Moreover,  the 
error  in  this  formula  affected  the  Helicoptere  quite  as 
much  as  the  aeroplane  system,  and  as  I  was  working  with 
the  view  of  ascertaining  the  relative  merits  of  the  two 
systems,  the  error,  although  considerable,  did  not  have  any 
influence  at  all  in  the  decision  which  I  arrived  at — namely, 
that  the  aeroplane  system  was  the  best.  The  machine 
that  I  thought  out  at  that  time  contemplated  superposed 
aeroplanes  of  very  great  length  from  port  to  starboard. 
The  size  in  the  other  direction  was  more  for  the  purpose 
of  preventing  a  rapid  fall  than  for  a  lifting  effect.  I  saw 
that  it  would  be  necessary  to  have  horizontal  fore  and  aft 
rudders  placed  a  long  distance  apart,  so  as  to  prevent  rapid 
pitching,  and  it  appeared  to  me  that  the  further  these 
rudders  were  apart,  the  easier  it  would  be  to  manoeuvre 
the  machine.  As  I  never  had  any  doubts  regarding  the 
efficiency  of  screw  propellers  working  in  the  air,  I  decided 
to  use  two  of  these  of  a  large  size  rotating  in  opposite 
directions.  Of  course,  all  this  speculation  was  theory  only, 
but  I  verified  it  later  on  by  actual  experiments  before 
I  built  my  machine,  and  it  is  very  gratifying  to  me  to 
know  that  all  the  successful  flying  machines  of  to-day  are 
built  on  the  lines  which  I  had  thought  out  at  that  time, 
and  found  to  be  the  best.  All  have  superposed  aeroplanes 


Viii  PREFACE. 

of  great  length  from  port  to  starboard,  all  have  fore  and 
aft  horizontal  rudders,  and  all  are  driven  with  screw 
propellers.  The  change  from  my  model  is  only  a  change 
in  the  framework  made  possible  by  dispensing  with  the 
boiler,  water  tank,  and  steam  engine.  Tn  this  little  work, 
I  have  dealt  at  considerable  length  with  air  currents,  the 
flight  of  birds,  and  the  behaviour  of  kites,  perhaps  at  the 
expense  of  some  repetitions  ;  as  the  resemblance  between 
kite  flying  and  the  soaring  of  birds  is  similar  in  many 
respects,  repetitions  are  necessary.  To  those  who  go  to 
sea  in  ships,  it  is  necessary  to  know  something  of  the 
currents  they  are  liable  to  encounter  ;  if  it  be  a  sailing  ship, 
certainly  a  knowledge  of  the  air  currents  is  of  the  greatest 
importance,  and  so  it  is  with  flying  machines.  If  flights 
of  any  considerable  distance  are  to  be  made,  the  machine  is 
liable  at  any  time  to  encounter  very  erratic  air  currents, 
and  it  has  been  my  aim  in  discussing  these  three  subjects — 
air  currents,  birds,  and  kites — to  bring  them  before  the 
would-be  navigators  of  the  air,  in  order  that  they  may 
anticipate  the  difficulties  they  have  to  deal  with  and 
be  ready  to  combat  them.  Then,  again,  there  has  been 
almost  an  infinite  amount  of  discussion  regarding  the 
soaring  of  birds  and  the  flying  of  kites.  Many  years 
ago,  after  reading  numerous  works  on  the  subject  of 
flight,  I  became  a  close  observer  myself,  and  always 
sought  in  my  travels  to  learn  as  much  as  possible.  I 
have  attempted  to  discuss  this  subject  in  simple  and 
easily  understood  language,  and  to  present  sufficient 
evidence  to  prevent  the  necessity  of  any  further  disputes. 
I  do  not  regard  what  I  have  said  as  a  theory,  but  simply 
as  a  plain  statement  of  absolute  and  easily  demonstrated 
facts.  During  the  last  few  years,  a  considerable  number 
of  text-books  and  scientific  treatises  have  been  written 
on  the  subject  of  artificial  flight,  the  most  elaborate  and 
by  far  the  most  reliable  of  these  being  the  "  Pocket-Book 
of  Aeronautics,"  by  Herman  W.  L.  Moedebeck,  Major 
und  battaillons  Kommandeur  im  Badischen  Fussartillerie 


PREFACE.  IX 

Regiment  No.  14  ;  in  collaboration  with  O.  Chanute 
and  others.  Translated  by  W.  Mansergh  Varley,  B.A., 
D.Sc.,  Ph.D.,  and  published  by  Whittaker  &  Co.  This 
work  does  not,  however,  confine  itself  altogether  to  flying 
machines,  but  has  a  great  deal  of  information  which  is  of 
little  or  no  value  to  the  builder  of  true  flying  machines ; 
moreover,  it  is  not  simple  enough  to  be  readily  understood 
by  the  majority  of  experimenters.  In  some  other  works 
which  I  have  recently  examined,  I  find  a  confusing  mass  of 
the  most  intricate  mathematical  calculations,  abounding  in 
an  almost  infinite  number  of  characters,  and  extending  over 
hundreds  of  pages,  but  on  a  close  examination  of  some  of 
the  deductions  arrived  at,  I  find  that  a  good  many  of  the 
mathematical  equations  are  based  on  a  mistaken  hypothesis, 
and  the  results  arrived  at  are  very  wide  of  the  truth.  I 
have  shown  several  diagrams  which  will  explain  what 
I  mean.  What  is  required  by  experimenters  in  flying 
machines — and  there  will  soon  be  a  great  number  of  them — 
is  a  treatise  which  they  can  understand,  and  which  requires 
no  more  delicate  instruments  than  a  carpenter's  2-foot  rule 
and  a  grocer's  scales.  The  calculations  relating  to  the  lift, 
drift,  and  the  skin  friction  of  an  aeroplane  are  extremely 
simple,  and  it  is  quite  possible  to  so  place  this  matter  that 
it  can  be  understood  by  anyone  who  has  the  least  smatter- 
ing of  mathematical  knowledge.  Mathematics  of  the 
higher  order  expressed  in  elaborate  formulae  do  very  well 
in  communications  between  college  professors — that  is,  if 
they  happen  to  be  agreed.  When,  however,  these  calcula- 
tions are  so  intricate  as  to  require  a  clever  mathematician 
a  whole  day  to  study  out  the  meaning  of  a  single  page, 
and  if  when  the  riddle  is  solved,  we  find  that  these 
calculations  are  based  on  a  fallacy,  and  the  results  in 
conflict  with  facts,  it  becomes  quite  evident  to  the  actual 
experimenter  that  they  are  of  little  value.  For  many 
years,  Newton's  law  was  implicitly  relied  upon.  Chanute, 
after  going  over  my  experimental  work,  wrote  that  Newton's 
law  was  out  as  20  is  to  1 — that  is,  that  an  aeroplane  would 


lift  twenty  times  as  much  in  practice  as  could  be  shown  by 
the  use  of  Newton's  formula.  Some  recent  experiments, 
which  I  have  made  myself,  at  extremely  high  velocities 
and  at  a  very  low  angle,  seem  to  demonstrate  that  the 
error  is  nearer  100  to  1  than  20  to  1.  It  will,  therefore, 
be  seen  how  little  this  subject  was  understood  until  quite 
recently,  and  even  now  the  mathematicians  who  write 
books  and  use  such  an  immense  amount  of  formulae,  do  not 
agree  by  any  means,  as  will  be  witnessed  by  the  mass  of 
conflicting  controversy  which  has  been  appearing  in 
Engineering  during  the  last  four  months.  When,- an 
aeroplane  placed  at  a  working  angle  of,  say,  1  in  99  is 
driven  through  the  air  at  a  high  velocity,  it,  of  course, 
pushes  the  air  beneath  it  downwards  at  one-tenth  part  of 
its  forward  velocity — that  is,  in  moving  10  feet,  it  pushes 
the  air  down  1  foot.  A  good  many  mathematicians  rely 
altogether  upon  the  acceleration  of  the  mass  of  air  beneath 
the  aeroplane  which  is  accelerated  by  its  march  through 
the  air,  the  value  of  this  acceleration  being  in  proportion  to 
the  square  of  the  velocity  which  is  imparted  to  it.  Suppose 
now  that  the  aeroplane  is  thin  and  well-made,  that  both 
top  and  bottom  sides  are  equally  smooth  and  perfect ;  not 
only  does  the  air  engaged  by  the  under  side  shoot  down- 
wards, but  the  air  also  follows  the  exact  contour  of 
the  top  side,  and  is  also  shot  downwards  with  the  same 
mean  velocity  as  that  passing  on  the  underneath  side,  so  if 
we  are  going  to  consider  the  lifting  effect  of  the  aeroplane, 
we  must  not  leave  out  of  the  equation,  the  air  above  the 
aeroplane,  which  has  quite  as  much  mass  and  the  same 
acceleration  imparted  to  it,  as  the  air  below  the  aeroplane. 
Even  calculations  made  on  this  basis  will  not  bring  the 
lifting  effect  of  an  aeroplane  up  to  what  it  actually  does  lift 
in  practice  ;  in  fact,  the  few  mathematicians  who  have  made 
experiments  themselves  have  referred  to  the  actual  lifting 
effect  of  aeroplanes  placed  at  a  low  angle  and  travelling  at 
a  high  velocity  as  being  unaccountable.  Only  a  few 
mathematicians  appear  to  have  a  proper  grasp  of  the 


subject.  However,  three  could  be  pointed  out  who  under- 
stand the  subject  thoroughly,  but  these  are  all  mathe- 
maticians of  the  very  highest  order — Lord  Kelvin,  Lord 
Rayleigh,  and  Professor  Langley.  In  placing  before  the 
public,  the  results  of  my  experiments  and  the  conclusions 
arrived  at,  it  is  necessary  to  show  the  apparatus  which  I 
employed,  otherwise  it  might  be  inferred  that  my  con- 
clusions were  guesswork,  or  mathematical  calculations  which 
might  or  might  not  be  founded  on  a  mistaken  hypothesis ; 
this  is  my  excuse  for  showing  my  boiler  and  engine,  my 
rotating  arm,  and  my  large  machine.  I  do  not  anticipate 
that  anyone  will  ever  use  a  steam  engine  again,  because 
any  form  of  a  boiler  is  heavy  ;  moreover,  the  amount  of 
fuel  required  is  much  greater  than  with  an  internal  com- 
bustion engine,  and  certainly  seven  times  as  much  water 
has  to  be  dealt  with.  However,  the  description  which 
I  am  giving  of  my  apparatus  will  demonstrate  that  I  had 
the  instruments  for  doing  the  experimental  work  that  I 
have  described  in  this  work.  In  the  Appendix  will  be 
found  a  description  of  my  machine,  and  some  of  my 
apparatus.  The  conclusions  which  I  arrived  at  were  written 
down  at  the  time  with  a  considerable  degree  of  care,  and 
are  of  interest  because  they  show  that,  at  that  date,  I  had 
produced  a  machine  that  lifted  considerably  more  than  its 
own  weight  and  had  all  of  the  essential  elements,  as  far  as 
superposed  aeroplanes,  fore  and  aft  horizontal  rudders,  and 
screw  propellers  were  concerned,  common  to  all  of  the 
successful  machines  which  have  since  been  made.  The 
fact  that  practically  no  essential  departure  has  been  made 
from  my  original  lines,  indicates  to  my  mind  that  I  had 
reasoned  out  the  best  type  of  a  machine  even  before  I 
commenced  a  stroke  of  the  work. 

I  have  to  thank  Mr.  Albert  T.  Thurston  for  reading  the 
proofs  of  this  work. 

H.  S.  M. 


CONTENTS. 


CHAPTER    I. 

PAGE 

Introductory 1 

CHAPTER  II. 
Air  Currents  and  the  Flight  of  Birds, .11 

CHAPTER   III. 
Flying  of  Kites, 25 

CHAPTER   IV. 
Principally  Relating  to  Screws, 31 

CHAPTER  V. 

Experiments  with  Apparatus  Attached  to  a  Rotating  Arm — Crystal 

Palace  Experiments 62 

CHAPTER  VI. 

Hints  as  to  the  Building  of  Flying  Machines — Steering  by  Means  of 

a  Gyroscope, 77 

CHAPTER   VII. 

The  Shape  and  Efficiency  of  Aeroplanes — The  Action  of  Aeroplanes 
and  the  Power  Required  Expressed  in  the  Simplest  Terms — Some 
Recent  Machines 99 

CHAPTER  VIII. 
Balloons, .''      .        .        .         .        .         .120 

APPENDIX  I .        .        .        .        .        .         .  126 

APPENDIX  II. — 

Recapitulation  of  Early  Experiments  —  Efficiency  of  Screw 
Propellers,  Steering,  Stability,  &c. — The  Comparative  Value 
of  Different  Motors  —  Engines  —  Experiments  with  Small 
Machines  Attached  to  a  Rotating  Arm, 130 

INDEX,  .  .  163 


INDEX  OF   ILLUSTRATIONS. 


FIG.  PAGE 

1.  Diagram  showing  the  reduction  of  the  projected  horizontal 

area,     .  .  .  .  .  .  t          f 

2.  Professor  Langley's  experiments,  ....           5 

3.  Eagles  balancing  themselves  on  an  ascending  current  of  air,     .         14 

4.  Air  currents  observed  in  Mid- Atlantic,  .  .             .             .16 

5.  Glassy  streaks  in  the  Bay  of  Antibes,      .  .             .             .17 

6.  Air  currents  observed  in  the  Mediterranean,      .  .             .18 

7.  The  circulation  of  air  produced  by  a  difference  in  temperature,         27 

8.  Kite  flying,  .             .             .             .             .             .29 

9.  Group  of  screws  and  other  objects  used  in  my  experiments,      .         32 

10.  Some  of  the  principal  screws  experimented  with,  .  .         32 

11.  The  three  best  screws,      ......         33 

12.  Apparatus  for  testing  the  thrust  of  screws,         .  .  .34 

13.  Apparatus  for  testing  the  direction  of  air  currents,        .  .         35 

14.  The  ends  of  screw  blades,  .  .  .  .  .36 

15.  The  manner  of  building  up  the  large  screws,      .  .  .39 

16.  A  fabric-covered  screw,    ......         40 

17.  The  hub  and  one  of  the  blades  of  the  screw  on  the  Farman 

machine,  .......         42 

18.  Section  of  screw  blades  having  radial  edges,       .  .  .43 

1 9.  Form  of  the  blade  of  a  screw  made  of  sheet  metal,         .  .         44 

20.  New  form  of  hub, .......         45 

21.  Small  apparatus  for  testing  fabrics  for  aeroplanes,         .  .         50 

22.  Apparatus   for   testing    the   lifting   effect   of  aeroplanes  and 

condensers,      ....  51 

23.  Apparatus  for  testing  aeroplanes,  condensers,  &c. ,  j  .52 

24.  Cross-sections  of  bars  of  wood,     .             *    •         .  *  .53 

25.  Sections  of  bars  of  wood, .             .             .             l  .54 

26.  A  flat  aeroplane  placed  at  different  angles,          .  55 

27.  Group  of  aeroplanes  used  in  experimental  research,  .  .         56 

28.  An  8-inch  aeroplane  which  did  very  well,            .  .  .57 

29.  Resistance  due  to  placing  objects  in  close  proximity  to  each 

other,   ........         58 

30.  Cross-section  of  condenser  tube  made  in  the  form  of  Philipps' 

sustainers,        .......         60 

31.  The  grouping  of  condenser  tubes  made  in  the  form  of  Philipps' 

sustainers,       t            .             .             .             .             .  ,  61 

32.  Machine  with  a  rotating  arm,      .....  63 

33.  A  screw  and  fabric-covered  aeroplane  in  position  for  testing,   .  64 

34.  The  rotating  arm  of  the  machine  with  a  screw  and  aeroplane 

attached,          .......         65 

35.  The   little   steam   engine   used    by   me   in   my   rotating  arm 

experiments,    .......         66 

36.  The  machine  attached  to  the  end  of  the  rotating  shaft,  .         68 
37-     Marking  off  the  dynamometer,     .....         69 
37a.  Right-  and  left-hand  four-blade  screws, .             .             .  .70 
38.     Apparatus  for  indicating  the  force  and  velocity  of  the  wind 

direct,.  .......         71 


XIV  INDEX    OF    ILLUSTRATIONS. 

FIG.  PAGE 

39.  Apparatus  for  testing  the  lifting  effect  of  aeroplanes,    .  .         73 

40.  Front  elevation  of  proposed  aeroplane  machine,  .  .         77 

41.  Side  elevation  of  proposed  aeroplane  machine,    .  .  .78 

42.  Plan  of  proposed  aeroplane  machine,       .  .  .  .79 

43.  Plan  of  a  helicopt^re  machine,     .....         82 

44.  Showing  the  position  of  the  blades  of  a  helicoptere  as  they  pass 

around  a  circle,  .  .  .  .  .  .83 

45.  System  of  splicing  and  building  up  wooden  members,    .  .         86 

46.  Cross-section  of  struts,      ......         86 

47.  Truss  suitable  for  use  with  flying  machines,        .  .  .87 

48.  The  paradox  aeroplane,    ......         88 

49.  The  Antoinette  motor,      ......         89 

50.  Section  showing  the  Antoinette  motor  as  used  in  the  Farman 

and  De  la  Grange  machines,  .  .  .  .  .90 

51.  Pneumatic  buffer,  ......         91 

52.  Gyroscope,  .......         94 

53.  Adjusting  the  lifting  effect,          .  .  .  .  .95 

54.  Showing  that  the  machine  could  be  tilted  in  either  direction 

by  changing  the  position  of  the  rudder,         .  .  .96 

55.  Adjusting  the  lifting  effect,          .  .  .  .  .97 

56.  Adjustment  of  the  rudders,          .....         98 

57.  Diagram  showing  the  evolution  of  a  wide  aeroplane,     .  .       102 

58.  In  a  recently  published  mathematical  treatise  on  aerodynamics 

an  illustration  is  shown,  representing  the  path  that  the  air 
takes  on  encountering  a  rapidly  moving  curved  aeroplane,         104 

59.  An  illustration  from  another  scientific  publication  also  on  the 

dynamics  of  flight,       ......       104 

60.  Another  illustration  from  the  same  work ,  .             .             .       105 

61.  The  shape  and  the  practical  angle  of  an  aeroplane,         .  .       105 

62.  An  aeroplane  of  great  thickness,  ....       106 

63.  Section  of  a  screw  blade  having  a  rib  on  the  back,          .  .       106 

64.  Shows  a  flat  aeroplane  placed  at  an  angle  of  45°,  .             .       107 

65.  The  aeroplane  here  shown  is  a  mathematical  paradox,  .       107 

66.  This  shows  fig.  65  with  a  section  removed,         .  .       107 

67.  Diagram  showing  real  path  of  a  bird,      .  .       108 

68.  The  De  la  Grange  machine  on  the  ground,          .  .             .111 

69.  The  De  la  Grange  machine  in  full  flight,  .             .             .111 

70.  Farman's  machine  in  flight,          .  .             .             .             .112 

71.  Bleriot's  machine,  .             .             .             .            .             .113 

72.  Santos  Dumont's  flying  machine,  .            .             .             .113 
72a.  Angles  and  degrees  compared,      .  .             .             .             .115 
726.  Diagram   showing  direction  of  the  air  with  a  thick   curved 

aeroplane,        .......       118 

72c.  Aeroplanes  experimented  with  by  Mr.  Horatio  Philipps,  .       118 

73.  The  enormous  balloon  "Villede  Paris,"  .  .  .123 

74.  Photograph  of  a  model  of  my  machine,  ....       130 

75.  The  faerie- covered  aeroplane  experimented  with,  .  .       131 

76.  The  forward  rudder  of  my  large  machine  showing  the  fabric 

attached  to  the  lower  side,     .  .  .       -^ -  .  .  131 

77.  View  of  the  track  used  in  my  experiments,         .  .  .  134 

78.  The  machine  on  the  track  tied  up  to  the  dynamometer,  .  135 

79.  Two  dynagraphs,  .......  136 

80.  The  outrigger  wheel  that  gave  out  and  caused  an  accident 

with  the  machine,        ......  137 

81.  Shows  the  broken  planks  and  the  wreck  that  they  caused,        .  138 

82.  The  condition  of  the  machine  after  the  accident,  .  .  139 

83.  This  shows  the  screws  damaged  by  the  broken  planks,  .  140 

84.  This  shows  a  form  of  outrigger  wheels  which  were  ultimately  used,  141 


INDEX    OF    ILLUSTRATIONS.  XV 

FIG.  PAGE 

85.  One  pair  of  my  compound  engines,  ....       142 

86.  Diagram  showing  the  path  that  the  air  has  to  take  in  passing 

between  superposed  aeroplanes  in  close  proximity  to  each 
other,  .  .  .  .  .  .  .  .144 

87.  Position  of  narrow  aeroplanes  arranged  so  that  the  air  has 

free  passage  between  them,    .....       145 

88.  The  very  narrow  aeroplanes  or  sustainers  employed  by  Mr. 

Philipps, .146 

89.  One  of  the  large  screws  being  hoisted  into  position,       .  .       149 

90.  Steam  boiler  employed  in  my  experiments,         .  .  .       157 

91.  The  burner  employed  in  my  steam  experiments,  .  .157 

92.  Count  Zeppelin's  aluminium-covered  airship  coming  out  of  its 

shed  on  Lake  Constance,        .                          .  .  .161 

93.  Count  Zeppelin's  airship  in  full  flight,    .             .  161 

94.  The  new  British  war  balloon  "  Dirigible "  No.  2,  .  .       162 

95.  The  Wright  aeroplane  in  full  flight,         .             .  .  .162 


ARTIFICIAL  AND  NATURAL  FLIGHT. 


CHAPTER    I. 
INTRODUCTORY. 

IT  has  been  my  aim  in  preparing  this  little  work  for 
publication  to  give  a  description  of  my  own  experimental 
work,  and  explain  the  machinery  and  methods  that  have 
enabled  me  to  arrive  at  certain  conclusions  regarding 
the  problem  of  flight.  The  results  of  my  experiments 
did  not  agree  with  the  accepted  mathematical  formulae  of 
that  time.  I  do  not  wish  this  little  work  to  be  considered  as 
a  mathematical  text-book;  I  leave  that  part  of  the  problem 
to  others,  confining  myself  altogether  to  data  obtained  by 
my  own  actual  experiments  and  observations.  During 
the  last  few  years,  a  considerable  number  of  text-books 
have  been  published.  These  have  for  the  most  part  been 
prepared  by  professional  mathematicians,  who  have  led 
themselves  to  believe  that  all  problems  connected  with 
mundane  life  are  susceptible  of  solution  by  the  use  of 
mathematical  formulae,  providing,  of  course,  that  the 
number  of  characters  employed  are  numerous  enough. 
When  the  Arabic  alphabet  used  in  the  English  language 
is  not  sufficient,  they  exhaust  the  Greek  also,  and  it  even 
appears  that  both  of  these  have  to  be  supplemented  some- 
times by  the  use  of  Chinese  characters.  As  this  latter 
supply  is  unlimited,  it  is  evidently  a  move  in  the  right 
direction.  Quite  true,  many  of  the  factors  in  the  problems 
with  which  they  have  to  deal  are  completely  unknown 
and  unknowable ;  still  they  do  not  hesitate  to  work  out 
a  complete  solution  without  the  aid  of  any  experimental 
data  at  all.  If  the  result  of  their  calculations  should  not 
agree  with  facts,  "bad  luck  to  the  facts."  Up  to  twenty 
years  ago,  Newton's  erroneous  law  as  relates  to  atmo- 


2  ARTIFICIAL    AND    NATURAL    FLIGHT. 

spheric  resistance  was  implicitly  relied  upon,  and  it  was 
not  the  mathematician  who  detected  its  error,  in  fact,  we 
have  plenty  of  mathematicians  to-day  who  can  prove  by 
formulae  that  Newton's  law  is  absolutely  correct  and 
unassailable.  It  was  an  experimenter  that  detected  the 
fault  in  Newton's  law.  In  one  of  the  little  mathematical 
treatises  that  I  have  before  me,  I  find  drawings  of  aero- 
planes set  at  a  high  and  impracticable  angle  with  dotted 
lines  showing  the  manner  in  which  the  writer  thinks  the 
air  is  deflected  on  coming  in  contact  with  them.  The 
dotted  lines  show  that  the  air  which  strikes  the  lower 
or  front  side  of  the  aeroplane,  instead  of  following  the 
surface  and  being  discharged  at  the  lower  or  trailing  edge, 
takes  a  totally  different  and  opposite  path,  moving  forward 
and  over  the  top  or  forward  edge,  producing  a  large  eddy 
of  confused  currents  at  the  rear  and  top  side  of  the  aero- 
plane. It  is  very  evident  that  the  air  never  takes  the 
erratic  path  shown  in  these  drawings ;  moreover,  the  angle 
of  the  aeroplane  is  much  greater  than  one  would  ever 
think  of  employing  on  an  actual  flying  machine.  Fully 
two  pages  of  closely  written  mathematical  formulae  follow, 
all  based  on  this  mistaken  hypothesis.  It  is  only  too 
evident  that  mathematics  of  this  kind  can  be  of  little  use 
to  the  serious  experimenter.  The  mathematical  equation 
relating  to  the  lift  and  drift  of  a  well-made  aeroplane  is 
extremely  simple;  at  any  practicable  angle  from  I  in  20 
to  1  in  5,  the  lifting  effect  will  be  just  as  much  greater 


Fig.  1. — Diagram  showing  the  reduction  of  the  projected  horizontal  area 
of  aeroplanes  due  to  raising  the  front  edge  above  the  horizontal — 
tt,  6,  shows  an  angle  of  1  in  4,  which  is  the  highest  angle  that  will 
ever  be  used  in  a  flying  machine,  and  this  only  reduces  the  projected 
area  about  2  per  cent.  The  line  c  b  shows  an  angle  of  1  in  8,  and 
this  only  reduces  the  projected  area  an  infinitesimal  amount.  As  the 
angle  of  inclination  is  increased,  the  projected  area  becomes  less  as 
the  versed  sineyrf  becomes  greater. 

than  the  drift,  as  the  width  of  the  plane  is  greater  than 
the  elevation  of  the  front  edge  above  the  horizontal — that 


INTRODUCTORY. 


is,  if  we  set  an  aeroplane  at  an  angle  of  1  in  10,  and 
employ  1  Ib.  pressure  for  pushing  this  aeroplane  forward, 
the  aeroplane  will  lift  10  Ibs.  If  we  change  the  angle 
to  1  in  16,  the  lift  will  be  16  times  as  great  as  the  drift. 
It  is  quite  true  that  as  the  front  edge  of  the  aeroplane 
is  raised,  its  projected  horizontal  area  is  reduced — that 
is,  if  we  consider  the  width  of  the  aeroplane  as  a  radius, 
the  elevation  of  the  front  edge  will  reduce  its  projected 
horizontal  area  just  in  the  proportion  that  the  versed  sine 
is  increased.  For  instance,  suppose  the  sine  of  the  angle 
to  be  one-sixth  of  the  radius,  giving,  of  course,  to  the 
aeroplane  an  inclination  of  1  in  6,  which  is  the  sharpest 
practical  angle,  this  only  reduces  the  projected  area  about 
2  per  cent.,  while  the  lower  and  more  practical  angles 
are  reduced  considerably  less  than  1  per  cent.  It  will, 
therefore,  be  seen  that  this  factor  is  so  small  that  it  may 
not  be  considered  at  all  in  practical  flight. 

Some  of  the  mathematicians  have  demonstrated  by 
formulae,  unsupported  by  facts,  that  there  is  a  consider- 
able amount  of  skin  friction  to  be  considered,  but  as  no 
two  agree  on  this  or  any  other  subject,  some  not  agreeing 
to-day  with  what  they  wrote  a  year  ago,  I  think  we 
might  put  down  all  of  their  results,  add  them  together, 
and  then  divide  by  the  number  of  mathematicians,  and 
thus  find  the  average  coefficient  of  error.  When  we 
subject  this  question  to  experimental  test,  we  find  that 
nearly  all  of  the  mathematicians  are  radically  wrong, 
Professor  Langley,  of  course,  excepted.  I  made  an  aero- 
plane of  hard  rolled  brass,  20  gauge ;  it  was  1  foot  wide 
and  dead  smooth  on  both  sides;  I  gave  it  a  curvature 
of  about  T\  inch  and  filed  the  edges,  thin  and  sharp.  I 
mounted  this  with  a  great  deal  of  care  in  a  perfectly 
horizontal  blast  of  air  of  40  miles  an  hour.  When  this 
aeroplane  was  placed  at  any  angle  between  1  in  8  and 
1  in  20,  the  lifting  effect  was  always  just  in  proportion  to 
its  angle.  The  distance  that  the  front  edge  was  raised 
above  the  horizontal,  as  compared  with  the  width  of 
the  aeroplane,  was  always  identical  with  the  drift  as 
compared  with  the  lift.  On  account  of  the  jarring  effect 
caused  by  the  rotation  of  the  screws  that  produced  the 
air  blast,  we  might  consider  that  all  of  the  articulated 
joints  about  the  weighing  device  were  absolutely  friction- 
less,  as  the  jar  would  cause  them  to  settle  into  the  proper 
position  quite  irrespective  of  friction.  I  was,  therefore, 


4  ARTIFICIAL    AND    NATURAL    FLIGHT. 

able  to  observe  very  carefully,  the  lift  and  the  drift.  As 
an  example  of  how  these  experiments  were  conducted,  I 
would  say  that  the  engine  employed  was  provided  with  a 
very  sensitive  and  accurate  governor;  the  power  trans- 
mission was  also  quite  reliable.  Before  making  these 
tests,  the  apparatus  was  tested  as  regards  the  drift,  with- 
out any  aeroplane  in  position,  and  with  weights  applied 
that  would  just  balance  any  effect  that  the  wind  might 
have  on  everything  except  the  aeroplane.  The  aeroplane 
was  then  put  in  position  and  the  other  system  of  weights 
applied  until  it  exactly  balanced,  all  the  levers  being 
rapped  in  order  to  eliminate  the  friction  in  their  joints. 
The  engine  was  then  started  and  weights  applied  just 
sufficient  to  counterbalance  the  lifting  effect  of  the  aero- 
plane, and  other  weights  applied  to  exactly  balance  the 
drift  or  the  tendency  to  travel  with  the  wind.  In  this 
way,  I  was  able  to  ascertain,  with  a  great  degree  of 
accuracy,  the  relative  difference  between  the  lift  and  drift. 
If  there  had  been  any  skin  friction,  even  to  the  extent  of 
2  per  cent.,  it  would  have  been  detected.  This  brass 
aeroplane  was  tested  at  various  angles,  and  always  gave 
the  same  results,  but  of  course  I  could  not  use  thick  brass 
aeroplanes  on  a  flying  machine ;  it  was  necessary  for  me 
to  seek  something  much  lighter.  I  therefore  conducted 
experiments  with  other  materials,  the  results  of  which 
are  given.  However,  with  a  well-made  wooden  aeroplane 
1  foot  wide  and  with  a  thickness  in  the  centre  of  TV  inch, 
I  obtained  results  almost  identical  with  those  of  the  very 
much  thinner  brass  aeroplane,  but  it  must  not  be  supposed 
that  in  practice  an  aeroplane  is  completely  without  friction. 
If  it  is  very  rough,  irregular  in  shape,  and  has  any  pro- 
jections whatsoever  on  either  the  top  or  bottom  side, 
there  will  be  a  good  deal  of  friction,  although  it  may  not, 
strictly  speaking,  be  skin  friction ;  still,  it  will  absorb  the 
power,  and  the  coefficient  of  this  friction  may  be  anything 
from  '05  to  '40.  These  experiments  with  the  brass  aero- 
plane demonstrated  that  the  lifting  effect  was  in  direct 
proportion  to  the  angle,  and  that  skin  friction,  if  it  exists 
at  all,  was  extremely  small,  but  this  does  not  agree  with 
a  certain  kind  of  reasoning  which  can  be  made  very 
plausible  and  is  consequently  generally  accepted. 

Writers  of  books,  as  a  rule,  have  always  supposed  that 
the  lifting  effect  of  an  aeroplane  was  not  in  proportion 
to  its  inclination,  but  in  proportion  to  the  square  of  the 


INTRODUCTORY.  5 

sine  of  the  angle.  In  order  to  make  this  matter  clear,  I 
will  explain.  Suppose  that  an  aeroplane  is  20  inches  wide 
and  the  front  edge  is  raised  1  inch  above  the  horizontal. 
In  ordinary  parlance  this  is,  of  course,  called  an  inclination 
of  1  in  20,  but  mathematicians  approach  it  from  a  different 
standpoint.  They  regard  the  width  of  the  aeroplane  as 
unity  or  the  radius,  and  the  1  inch  that  the  front  edge 
is  raised  as  a  fraction  of  unity.  The  geometrical  name 
of  this  1  inch  is  the  sine  of  the  angle — that  is,  it  is  the 
sine  of  the  angJe  at  which  the  aeroplane  is  raised  above 
the  horizontal.  Suppose,  now,  that  we  have  another 
identical  aeroplane  and  we  raise  the  front  edge  2  inches 
above  the  horizontal.  It  is  very  evident  that,  under 
these  conditions,  the  sine  of  the  angle  will  be  twice  as 
much,  and  that  the  square  of  the  sine  of  the  angle  will 
be  four  times  as  great.  All  the  early  mathematicians, 
and  some  of  those  of  the  present  day,  imagine  that  the 
lift  must  be  in  proportion  to  the  square  of  the  sine  of 
the  angle.  They  reason  it  out  as  follows : — If  an  aero- 
plane is  forced  through  the  air  at  a  given  velocity,  the 
aeroplane  in  which  the  sine  of  the  angle  is  2  inches  will 
push  the  air  down  with  twice  as  great  a  velocity  as  the 
one  in  which  the  sine  of  the  angle  is  only  1  inch,  and 
as  the  force  of  the  wind  blowing  against  a  normal  plane 
increases  as  the  square  of  the  velocity,  the  same  law  holds 


Fig.  2. — Professor  Langley's  experiments — a,  end  of  the  rotating  arm; 
6,  brass  plane  weighing  1  lb.  ;  c  c,  spiral  springs.  When  the  arm  was 
driven  through  the  air,  in  the  direction  shown,  the  plane  assumed 
approximately  a  horizontal  position,  and  the  pull  on  the  springs  c  c 
was  reduced  from  1  lb.  to  1  oz. 

good  in  driving  a  normal  plane  through  still  air.     From 
this  reasoning,  one  is  led  to  suppose  that  an  aeroplane  set 


b  ARTIFICIAL    AND    NATURAL    FLIGHT. 

at  an  angle  of  1  in  10  will  lift  four  times  as  much  as  one 
in  which  the  inclination  is  only  1  in  20,  but  experiments 
have  shown  that  this  theory  is  very  wide  of  the  truth. 
There  are  dozens  of  ways  of  showing,  by  pure  mathe- 
matics, that  Newton's  law  is  quite  correct ;  but  in  building 
a  flying  machine  no  theory  is  good  that  does  not  correspond 
with  facts,  and  it  is  a  fact,  without  any  question,  that  the 
lifting  effect  of  an  aeroplane,  instead  of  increasing  as  the 
square  of  the  sine  of  the  angle,  only  increases  as  the  angle. 
Lord  Kelvin,  when  he  visited  my  place,  was,  I  think,  the 
first  to  mention  this,  and  point  out  that  Newton's  law  was 
at  fault.  Professor  Langley  also  pointed  out  the  fallacy 
of  Newton's  law,  and  other  experimenters  have  found  that 
the  lifting  effect  does  not  increase  as  the  square  of  the 
sine  of  the  angle.  In  order  to  put  this  matter  at  rest, 
Lord  Rayleigh,  who,  I  think  we  must  all  admit,  would 
not  be  likely  to  make  a  mistake,  made  some  very  simple 
experiments,  in  which  he  demonstrated  that  two  aero- 
planes, in  which  we  may  consider  the  sine  of  the  angle 
to  be  £  inch,  lifted  slightly  more  than  a  similar  aeroplane 
in  which  the  sine  of  the  angle  was  only  |  inch.  Of  course, 
Lord  Rayleigh  did  not  express  it  in  inches,  but  in  term  of 
the  radius.  His  aeroplanes  were,  however,  very  small.  We 
can  rely  upon  it  that  the  lifting  effect  of  an  aeroplane  at 
any  practical  angle,  everything  else  being  equal,  increases  in 
direct  proportion  to  the  angle  of  the  inclination.  In  this 
little  work,  I  have  attempted  to  make  things  as  simple 
as  possible ;  it  has  not  been  written  for  mathematicians, 
and  I  have,  therefore,  thought  best  to  express  myself  in 
inches  instead  of  in  degrees.  If  I  write,  "  an  inclination 
of  1  in  20,"  everyone  will  understand  it,  and  only  a 
carpenter's  2-foot  rule  is  required  to  ascertain  what  the 
angle  is.  Then,  again,  simple  measurements  make  cal- 
culations much  simpler,  and  the  lifting  effect  is  at  once 
understood  without  any  computations  being  necessary. 
If  the  angles  are  expressed  in  degrees  and  minutes,  it 
is  necessary  to  have  a  protractor  or  a  text-book  in .  order 
to  find  out  what  the  inclination  really  is.  When  I  made 
my  experiments,  I  only  had  in  mind  the  obtaining  of 
correct  data,  to  enable  me  to  build  a  flying  machine  that 
would  lift  itself  from  the  ground.  At  that  time  I  was 
extremely  busy,  and  during  the  first  two  years  of  my 
experimental  work,  I  was  out  of  England  fourteen  months. 
After  having  made  my  apparatus,  I  conducted  my  experi- 


INTRODUCTORY.  7 

ments  rather  quickly,  it  is  true,  but  I  intended  later  on 
to  go  over  them  systematically  and  deliberately,  make 
many  more  experiments,  write  down  results,  and  prepare 
some  account  of  them  for  publication.  However,  the 
property  where  I  made  these  experiments  was  sold  by 
the  company  owning  it,  and  my  work  was  never  finished, 
so  I  am  depending  on  the  scraps  of  data  that  were  written 
down  at  the  time.  I  am  also  publishing  certain  observa- 
tions that  I  wrote  down  shortly  after  I  had  succeeded  in 
lifting  more  than  the  weight  of  my  machine.  I  think 
that  the  experiments  which  I  made  with  an  aeroplane 
only  8  inches  wide  will  be  found  the  most  reliable.  All 
the  machinery  was  running  'smoothly,  and  the  experiments 
were  conducted  with  a  considerable  degree  of  care.  In 
making  any  formula  on  the  lifting  effect  of  the  aeroplane, 
it  should  be  based  on  what  was  accomplished  with  the 
8-inch  plane.  Only  a  few  experiments  were  made  to 
ascertain  the  relative  value  of  planes  of  different  widths. 
However,  I  think  we  must  all  admit  that  a  wide  plane 
is  not  as  economical  in  power  as  a  narrow  one.  In  order 
to  make  this  matter  plain,  suppose  that  we  have  one 
aeroplane  placed  at  such  an  angle  that  it  will  lift  2  Ibs. 
per  square  foot  at  a  velocity  of  40  miles  an  hour;  it  is 
very  evident  that  the  air  just  at  the  rear  of  this  aeroplane 
would  be  moving  downward  at  a  velocity  corresponding 
to  the  acceleration  imparted  to  it  by  the  plane.  If  we 
wish  to  obtain  lifting  effect  on  this  air  by  another  plane 
of  exactly  the  same  width,  we  shall  have  to  increase  its 
inclination  in  order  to  obtain  the  same  lifting  effect,  and, 
still  further,  it  will  be  necessary  to  use  more  power  in 
proportion  to  the  load  lifted.  If  a  third  aeroplane  is  used, 
it  must  be  placed  at  an  angle  that  will  impart  additional 
acceleration  to  the  air,  and  so  on.  Each  plane  that  we 
add  will  have  to  be  placed  at  a  sharper  angle,  and  the 
power  required  will  be  just  in  proportion  to  the  average 
angle  of  all  the  planes.  As  the  action  of  a  wide  aeroplane 
is  identical  with  that  of  numerous  narrow  ones  placed  in 
close  proximity  to  each  other,  it  is  very  evident  that  a 
wide  aeroplane  cannot  be  as  efficient  in  proportion  to  its 
width  as  a  narrow  one.  I  have  thought  the  matter  over, 
and  I  should  say  that  the  lifting  effect  of  a  flat  aero- 
plane increases  rather  faster  than  the  square  root  of 
its  width.  This  will,  at  least,  do  for  a  working  hypo- 
thesis. Every  flying  machine  must  have  what  we  will 


0  ARTIFICIAL    AND    NATURAL    FLIGHT. 

call  "  a  length  of  entering  edge " — that  is,  the  sum  of 
entering  edges  of  all  the  aeroplanes  must  bear  a  fixed 
relation  to  the  load  carried.  If  a  machine  is  to  have  its 
lifting  effect  doubled,  it  is  necessary  to  have  the  length 
of  entering  edge  twice  as  long.  This  additional  length 
may,  of  course,  be  obtained  by  superposed  planes,  but  as 
we  may  assume  that  a  large  aeroplane  will  travel  faster 
than  a  small  one,  increased  velocity  will  compensate  in 
some  degree  for  the  greater  width  of  larger  aeroplanes. 
By  careful  study  of  the  experiments  which  I  have  made, 

1  think  it  is  quite  safe  to  state  that  the  lifting  effect  of 
well-made  aeroplanes,  if  we  do  not  take  into  consideration 
the   resistance   due   to   the   framework   holding   them   in 
position,  increases  as  the  square  of  their  velocity.     Double 
their   speed  and  they  give  four  times  the  lifting  effect. 
The  higher  the  speed,  the  smaller  the  angle  of  the  plane, 
and   the   greater   the   lifting   effect   in  proportion  to  the 
power  employed.     When  we  build  a  steamship,  we  know 
that  its  weight  increases  as  the  cube  of  any  one  of  its 
dimensions — that  is,  if  the  ship  is  twice   as  long,  twice 
as  wide,  and  twice  as  deep  it  will  carry  eight  times  as 
much ;    but   at   the   very   best,   with   even   higher   speed, 
the  load  carried   by  a  flying  machine  will  only  increase 
with  the  square  of  any  one  of  its  dimensions,  or  perhaps 
still  less.     No  matter  whether  it  is  a  ship,  a  locomotive, 
or  a  flying  machine  that  we  wish  to  build,  we  must  first 
of  all  consider  the  ideal,  and  then  approximate  it  as  closely 
as  possible  with  the  material  at  hand.     Suppose  it  were 
possible  to  make  a  perfect  screw,  working  without  friction, 
and  that  its  weight  should  only  be  that  of  the  surrounding 
air ;  if  it  should  be  200  feet  in  diameter,  the  power  of  one 
man,  properly  applied,  would  lift  him  into  the  air.     This 
is  because  the  area  of  a  circle  200  feet  in  diameter  is  so 
great  that  the  weight  of  a  man  would  not  cause  it  to  fall 
through  the  air  at  a  velocity  greater  than  the  man  would 
be  able  to  climb  up  a  ladder.     If  the  diameter  should  be 
increased  to  400  feet,  then  a  man  would  be  able  to  carry 
a  passenger  as  heavy  as  himself  on  his  flying  machine,  and 
if  we  should   increase  it  still  further,  to  2,000  feet,  the 
weight  of  a  horse  could  be  sustained  in  still  air  by  the 
power  which  one  man   could   put  forth.      On   the  other 
hand,  if  we  should  reduce  the  diameter  of  the  screw  to 
20  feet,  then  it  would  certainly  require  the  power  of  one 
horse  to  lift  the  weight  of  one  man,  and,  if  we  made  the 


INTRODUCTORY. 


screw  small  enough,  it  might  even  require  the  power  of 
100  horses  to  lift  the  same  weight.  It  will,  therefore, 
be  seen  that  everything  depends  upon  the  area  of  the 
air  engaged,  and  in  designing  a  machine  we  should  seek 
to  engage  as  much  air  as  possible,  so  long  as  we  can 
keep  down  the  weight.  Suppose  that  a  flying  machine 
should  be  equipped  with  a  screw  10  feet  in  diameter, 
with  a  pitch  of  6  feet,  and  that  the  motor  developed 
40  horse-power  and  gave  the  screw  1,000  turns  a  minute, 
producing  a  screw  thrust,  we  will  say,  of  about  220  Ibs. 
If  we  should  increase  the  diameter  of  the  screw  to  20  feet, 
and  if  it  had  the  same  pitch  and  revolved  at  the  same 
rate,  it  would  require  four  times  as  much  power  and 
would  give  four  times  as  much  screw  thrust,  because  the 
area  of  the  disc  increases  as  the  square  of  the  diameter. 
Suppose,  now,  that  we  should  reduce  the  pitch  of  the 
screw  to  3  feet,  we  should  in  this  case  engage  four  times 
as  much  air,  and  double  the  screw  thrust  without  using 
any  more  power — that  is,  assuming  that  the  machine  is 
stationary  and  that  the  full  power  of  the  engine  is  being 
used  for  accelerating  the  air.  The  advantages  of  a  large 
screw  will,  therefore,  be  obvious.  I  have  been  unable  to 
obtain  correct  data  regarding  the  experiments  which  have 
taken  place  with  the  various  machines  on  the  Continent. 
I  have,  however,  seen  these  machines,  and  I  should  say 
when  they  are  in  flight,  providing  that  the  engine  develops 
40  horse-power,  that  fully  28  horse-power  is  lost  in  screw 
slip,  and  the  remainder  in  forcing  the  machine  through 
the  air.  These  machines  weigh  1,000  Ibs.  each,  and  their 
engines  are  said  to  be  50  horse-power.  The  lifting  effect, 
therefore,  per  horse-power  is  20  Ibs.  If  the  aeroplanes 
were  perfect  in  shape  and  set  at  a  proper  angle,  and  the 
resistance  of  the  framework  reduced  to  a  minimum,  the 
same  lifting  effect  ought  to  be  produced  with  an  expendi- 
ture of  less  than  half  this  amount  of  power,  providing, 
of  course,  that  the  screw  be  of  proper  dimensions.  It  is 
said  that  Professor  Langley  and  Mr.  Horatio  Philipps,  by 
eliminating  the  factor  of  friction  altogether,  or  by  not 
considering  it  in  their  calculations,  have  succeeded  in 
lifting  at  the  rate  of  200  Ibs.  per  horse-power.  The 
apparatus  they  employed  was  very  small.  The  best  I 
ever  did  with  my  very  much  larger  apparatus — and 
I  only  did  it  on  one  occasion — was  to  carry  133  Ibs.  per 
horse -power.  In  my  large  machine  experiments,  I  was 


10  ARTIFICIAL    AND    NATURAL    FLIGHT. 

amazed  at  the  tremendous  amount  of  power  necessary  to 
drive  the  framework  and  the  numerous  wires  through  the 
air.  It  appeared  to  me,  from  these  experiments,  that 
the  air  resisted  very  strongly  being  cut  up  by  wires.  I 
expected  to  raise  my  machine  in  the  air  by  using  only 
100  horse-power,  and  my  first  condenser  was  made  so 
that  it  did  actually  condense  water  enough  to  supply 
100  horse-power,  but  the  framework  offered  such  a  tre- 
mendous resistance  that  I  was  compelled  to  strengthen 
all  of  the  parts,  make  the  machine  heavier,  and  increase 
the  boiler  pressure  and  piston  speed  until  I  actually  ran 
it  up  to  362  horse-power.  This,  however,  was  not  the 
indicated  horse-power.  It  was  arrived  at  by  multiplying 
the  pitch  of  the  screws,  in  feet,  by  the  number  of  turns 
that  they  made  in  a  minute,  and  by  the  screw  thrust  in 
pounds,  and  then  dividing  the  product  by  the  conventional 
unit  33,000.  I  have  no  doubt  that  the  indicated  horse- 
power would  have  been  fully  400.  On  one  occasion  I 
ran  my  machine  over  the  track  with  all  the  aeroplanes 
removed.  I  knew  what  steam  pressure  was  required  to 
run  my  machine  with  the  aeroplanes  in  position  at  a  speed 
of  40  miles  an  hour.  With  the  planes  removed,  it  still 
required  a  rather  high  steam  pressure  to  obtain  this 
velocity,  but  I  made  no  .note  at  the  time  of  the  exact 
difference.  It  was  not,  however,  by  any  means  so  great 
as  one  would  have  supposed.  From  the  foregoing,  it  will 
be  seen  how  necessary  it  is  to  consider  atmospheric  resist- 
ance. Although  I  do  not  expect  that  anyone  will  ever 
again  attempt  to  make  a  flying  machine  driven  by  a  steam 
engine,  still,  I  have  thought  best  to  give  a  short  and  concise 
description  of  my  engine  and  boiler,  in  order  that  my 
readers  may  understand  what  sort  of  an  apparatus  I 
employed  to  obtain  the  data  I  am  now,  for  the  first  time, 
placing  before  the  public.  A  full  description  of  everything 
relating  to  the  motor  power  was  written  down  at  the  time, 
and  has  been  carefully  preserved.  An  abridgement  of  this 
will  be  found  in  the  Appendix. 


11 


CHAPTER  II. 
AIR  CURRENTS  AND  THE  FLIGHT  OF  BIRDS. 

Ix  Mr.  Darwin's  "  Voyage  of  the  Beagle  "  I  find  : — 

"  When  the  condors  are  wheeling  in  a  flock  round  and 
round  any  spot  their  flight  is  beautiful.  Except  when 
rising  from  the  ground,  I  do  not  remember  ever  having 
seen  one  of  these  birds  flap  its  wings.  Near  Lima  I 
watched  several  for  nearly  half  an  hour,  without  taking 
off  my  eyes ;  they  moved  in  large  curves,  sweeping  in 
circles,  descending  and  ascending  without  giving  a  single 
flap.  As  they  glided  close  over  my  head  I  intently  watched 
from  an  oblique  position,  the  outlines  of  the  separate  and 
great  terminal  feathers  of  each  wing,  and  these  separate 
feathers,  if  there  had  been  the  least  vibratory  movement, 
would  have  appeared  as  if  blended  together;  but  they 
were  seen  distinct  against  the  blue  sky." 

Man  is  essentially  a  land  animal,  and  it  is  quite  possible 
if  Nature  had  not  placed  before  him  numerous  examples 
of  birds  and  insects  that  are  able  to  fly,  he  would  never 
have  thought  of  attempting  it  himself.  But  birds  are  very 
much  in  evidence,  and  mankind  from  the  very  earliest 
times  has  not  only  admired  the  ease  and  rapidity  with 
which  they  are  able  to  move  from  place  to  place,  but  has 
always  aspired  to  imitate  them.  The  number  of  attempts 
that  have  been  made  to  solve  this  problem  has  been  very 
great ;  but  it  was  not  until  quite  recently  that  science  and 
mechanics  had  advanced  far  enough  to  put  in  the  hands 
of  experimenters  suitable  material  to  attack  the  problem. 
Perhaps  nothing  better  has  ever  been  written  regarding 
our  aspirations  to  imitate  the  flight  of  birds  than  what 
Prof.  Langley  has  said  : — 

"  Nature  has  made  her  flying  machine  in  the  bird,  which 
is  nearly  a  thousand  times  as  heavy  as  the  air  its  bulk 
displaces,  and  only  those  who  have  tried  to  rival  it  know 
how  inimitable  her  work  is,  for  '  the  way  of  a  bird  in  the 
air'  remains  as  wonderful  to  us  as  it  was  to  Solomon, 
and  the  sight  of  the  bird  has  constantly  held  this  wonder 
before  men's  eyes,  and  in  some  men's  minds,  and  kept  the 


12  ARTIFICIAL   AND    NATURAL    FLIGHT. 

flame  of  hope  from  utter  extinction,  in  spite  of  long  dis- 
appointment. I  well  remember  how,  as  a  child,  when  lying 
in  a  New  England  pasture,  I  watched  a  hawk  soaring  far 
up  in  the  blue,  and  sailing  for  a  long  time  without  any 
motion  of  its  wings,  as  though  it  needed  no  work  to  sustain 
it,  but  was  kept  up  there  by  some  miracle.  But,  however 
sustained,  I  saw  it  sweep,  in  a  few  seconds  of  its  leisurely 
flight,  over  a  distance  that  to  me  was  encumbered  with 
every  sort  of  obstacle,  which  did  not  exist  for  it.  The 
wall  over  which  I  had  climbed  when  I  left  the  road,  the 
ravine  I  had  crossed,  the  patch  of  undergrowth  through 
which  I  had  pushed  my  way — all  these  were  nothing  to 
the  bird — and  while  the  road  had  only  taken  me  in  one 
direction,  the  bird's  level  highway  led  everywhere,  and 
opened  the  way  into  every  nook  and  corner  of  the  land- 
scape. How  wonderfully  easy,  too,  was  its  flight.  There 
was  not  a  flutter  of  its  pinions  as  it  swept  over  the  field, 
in  a  motion  which  seemed  as  effortless  as  that  of  its 
shadow." 

During  the  last  50  years  a  great  deal  has  been  said  and 
written  in  regard  to  the  flight  of  birds ;  no  other  natural 
phenomenon  has  excited  so  much  interest  and  been  so 
imperfectly  understood.  Learned  treatises  have  been 
written  to  prove  that  a  bird  is  able  to  develop  from  ten 
to  twenty  times  as  much  power  for  its  weight  as  other 
animals,  while  other  equally  learned  works  have  shown 
most  conclusively  that  no  greater  amount  of  energy  is 
exerted  by  a  bird  in  flying  than  by  land  animals  in 
running  or  jumping. 

Prof.  Langley,  who  was  certainly  a  very  clever  observer 
and  a  mathematician  of  the  first  order,  in  discussing  the 
subject  relating  to  the  power  exerted  by  birds  in  flight  and 
the  old  formula  relating  to  the  subject,  expresses  himself 
as  follows : — 

"  After  many  years  and  in  mature  life,  I  was  brought 
to  think  of  these  things  again,  a,nd  to  ask  myself  whether 
the  problem  of  artificial  flight  was  as  hopeless  and  as 
absurd  as  it  was  then  thought  to  be.  Nature  had  solved 
it,  and  why  not  man?  Perhaps  it  was  because  he  had 
begun  at  the  wrong  end,  and  attempted  to  construct 
machines  to  fly  before  knowing  the  principles  on  which 
flight  rested.  I  turned  for  these  principles  to  my  books 
and  got  no  help.  Sir  Isaac  Newton  had  indicated  a  rule 
for  finding  the  resistance  to  advance  through  the  air, 


AIR    CURRENTS    AND    THE    FLIGHT    OF    BIRDS.  13 

which  seemed,  if  correct,  to  call  for  enormous  mechanical 
power,  and  a  distinguished  French  mathematician  had 
given  a  formula  showing  how  rapidly  the  power  must 
increase  with  the  velocity  of  flight,  and  according  to 
which  a  swallow,  to  attain  a  speed  it  is  known  to  reach, 
must  be  possessed  of  the  strength  of  a  man. 

"  Remembering  the  effortless  flight  of  the  soaring  bird, 
it  seemed  that  the  first  thing  to  do  was  to  discard  rules 
which  led  to  such  results,  and  to  commence  new  experi- 
ments, not  to  build  a  flying  machine  at  once,  but  to  find 
the  principles  upon  which  one  should  be  built;  to  find, 
for  instance,  with  certainty  by  direct  trial  how  much 
horse-power  was  needed  to  sustain  a  surface  of  .given 
weight  by  means  of  its  motion  through  the  air." 

There  is  no  question  but  what  a  bird  has  a  higher 
physical  development,  as  far  as  the  generation  of  power 
is  concerned,  than  any  other  animal  we  know  of.  Never- 
theless, I  think  that  everyone  who  has  made  a  study  of 
the  question  will  agree  that  some  animals,  such  as  hares 
and  rabbits,  exert  quite  as  much  power  in  running,  in 
proportion  to  their  weight,  as  a  sea-gull  or  an  eagle  does 
in  flying. 

The  amount  of  power  which  a  land  animal  has  to  exert 
is  always  a  fixed  and  definite  quantity.  If  an  animal 
weighing  100  Ibs.  has  to  ascend  a  hill  100  feet  high,  it 
always  means  the  development  of  10,000  foot-lbs.  With 
a  bird,  however,  there  is  no  such  thing  as  a  fixed  quantity. 
If  a  bird  weighing  100  Ibs.  should  raise  itself  into  the  air 
100  feet  during  a  perfect  calm,  the  amount  of  energy 
developed  would  be  10,000  foot  Ibs.  plus  the  slip  of  the 
wings.  But,  as  a  matter  of  fact,  the  air  in  which  a  bird 
flies  is  never  stationary,  as  I  propose  to  show  ;  it  is  always 
moving  either  up  or  down,  and  soaring  birds,  by  a  very 
delicate  sense  of  feeling,  always  take  advantage  of  a  rising 
column.  If  a  bird  finds  itself  in  a  column  of  air  which  is 
descending,  it  is  necessary  for  it  to  work  its  wings  very 
rapidly  in  order  to  prevent  a  descent  to  the  earth. 

I  have  often  observed  the  flight  of  hawks  and  eagles. 
They  seem  to  glide  through  the  air  with  hardly  any  move- 
ment of  their  wings.  Sometimes,  however,  they  stop  and 
hold  themselves  in  a  stationary  position  directly  over  a 
certain  spot,  carefully  watching  something  on  the  earth 
immediately  below.  In  such  cases  they  often  work  their 
wings  with  great  rapidity,  evidently  expending  an  enormous 


14 


ARTIFICIAL   AND    NATURAL    FLIGHT. 


amount  of  energy.  When,  however,  they  cease  to  hover 
and  commence  to  move  again  through  the  air,  they  appear 
to  keep  themselves  at  the  same  height  with  an  almost 
imperceptible  expenditure  of  power. 

Many  unscientific  observers  of  the  flight  of  birds  have 


Fig.  3. — While  in  the  Pyrenees  I  often  observed  eagles  balancing  them- 
selves on  an  ascending  current  of  air  produced  by  the  wind  blowing 
over  large  masses  of  rock. 

imagined  that  a  wind  or  a  horizontal  movement  of  the  air 
is  all  that  is  necessary  to  sustain  the  weight  of  a  bird  in 
the  air  after  the  manner  of  a  kite.  If,  however,  the  wind, 
which  is  only  air  in  motion,  should  be  blowing  everywhere 
at  exactly  the  same  velocity,  and  in  the  same  direction — 


AIR    CURRENTS    AND    THE    FLIGHT    OF    BIRDS.  15 

horizontally — it  would  offer  no  more  sustaining  power  to  a 
bird  than  a  dead  calm,  because  there  is  nothing  to  prevent 
the  body  of  the  bird  from  being  blown  along  with  the  air, 
and  whenever  it  attained  the  same  velocity  as  the  air,  no 
possible  arrangement  of  the  wings  could  prevent  it  from 
falling  to  the  earth. 

It  is  well  known  that  only  a  short  distance  above-  the 
earth's  surface,  say  30  or  40  miles,  we  find  an  extremely 
low  temperature  sometimes  referred  to  as  interstellar 
temperature  or  absolute  zero.  In  order  to  illustrate  the 
extremely  low  temperature  of  space,  I  would  cite  the 
following  instance : — 

One  evening,  in  the  State  of  Ohio,  a  farmer  saw  a  very 
brilliant  meteor ;  it  struck  in  one  of  his  fields  not  more 
than  100  feet  from  his  house.  He  at  once  rushed  to  the 
spot,  and,  pushing  his  arm  down  the  hole,  succeeded  in 
touching  it ;  but  he  very  quickly  withdrew  his  hand,  as  he 
found  it  extremely  hot.  Some  of  the  neighbours  rushed 
to  the  spot,  and  he  told  them  what  had  occurred,  where- 
upon one  of  them  put  his  hand  in  the  hole,  expecting  to  be 
burnt,  but,  much  to  his  surprise,  the  tips  of  his  wet  fingers 
were  instantly  frozen  to  the  meteor.  The  meteor  had  been 
travelling  at  such  an  exceedingly  high  velocity  that  the 
resistance  of  the  intensely  cold  and  highly  attenuated  outer 
atmosphere  was  sufficient  to  bring  its  temperature  up  to 
the  melting  point  of  iron  ;  but  the  heat  did  not  have  time 
to  pass  into  the  interior,  it  only  extended  inwards  perhaps 
|  inch,  so  that  when  the  meteor  came  to  a  state  of  rest, 
the  heat  of  the  exterior  was  soon  absorbed  by  the  intensely 
cold  interior,  thus  reducing  the  surface  to  a  temperature 
much  below  any  natural  temperature  that  we  find  at  the 
surface  of  the  earth. 

Nothing  can  be  more  certain  than  that  the  temperature 
is  extremely  low  a  slight  distance  above  the  earth's  surface. 
As  the  air  near  the  earth  never  falls  in  temperature  to 
anything  like  the  absolute  zero,  it  follows  that  there  is  a 
constant  change  going  on,  the  relatively  warm  air  near  the 
surface  of  the  earth  always  ascending,  and,  in  some  cases, 
doing  sufficient  work  in  expanding  to  render  a  portion  of 
the  water  it  contains  visible,  forming  clouds,  rain,  or  snow, 
while  the  very  cold  air  is  constantly  descending  to  take 
the  place  of  the  rising  column  of  warm  air.  I  have  noticed 
a  considerable  degree  of  regularity  in  the  movement  of  the 
air,  especially  at  a  long  distance  from  land,  where  the 


L6 


ARTIFICIAL    AND    NATURAL    FLIGHT. 


regularity  of  the  up  and  down  currents  is,  at  times,  very 
marked. 

On  one  occasion  while  crossing  the  Atlantic  in  fine 
weather  I  noticed,  some  miles  directly  ahead  of  the  ship, 
a  long  line  of  glassy  water.  Small  waves  indicated  that 
the  wind  was  blowing  in  the  exact  direction  in  which  the 
ship  was  moving,  and  as  we  approached  the  glassy  line, 
the  waves  became  smaller  and  smaller  until  they  com- 
pletely disappeared  in  a  mirror-like  surface,  which  was 
about  300  or  400  feet  wide,  and  extended  both  to  the 
port  and  starboard  in  approximately  a  straight  line  as 
far  as  the  eye  could  reach.  After  passing  the  centre  of 


Fig.  4.  —  Air  currents  observed  in  mid  Atlantic,  warm  air  ascending  at 
a,  a,  a,  and  cold  air  descending  at  b,  b,  b.  c,  c,  c  represent  the 
lines  where  the  waves  were  the  largest. 


this  zone,  I  noticed  that  small  waves  began  to  show  them- 
selves, but  in  the  exact  opposite  direction  to  those  through 
which  we  had  already  passed,  and  these  waves  became 
larger  and  larger  for  nearly  half  an  hour.  Then  they 
began  to  get  gradually  smaller,  when  I  observed  another 
glassy  line  directly  ahead  of  the  ship.  As  we  approached 
it,  the  waves  again  completely  disappeared,  but  after  passing 
through  it,  the  wind  was  blowing  in  the  opposite  direction, 
and  the  waves  increased  in  size  exactly  in  the  same  manner 
that  they  had  diminished  on  the  opposite  side  of  the  glassy 
streak  (Fig.  4). 

This,  of  course,  shows  that  directly  over  the  centre  of 


AIR    CURRENTS    AND    THE    FLIGHT    OF    BIRDS. 


17 


the  first  glassy  streak,  the  air  was  meeting  from  both 
sides  and  ascending  in  practically  a  straight  line  from  the 
surface  of  the  water,  and  then  spreading  out  high  above 
the  sea,  setting  up  a  light  wind  in  both  directions. 

I  spent  the  winter  of  1890-91  on  the  Riviera,  between 
Hyeres  les  Palmiers  and  Monte  Carlo.  The  weather  for 
the  most  part  was  very  fine,  and  I  often  had  the  oppor- 
tunity of  observing  the  peculiar  phenomena  which  I  had 
already  noticed  in  the  Atlantic,  only  on  a  much  smaller 
scale.  Whereas,  in  the  Atlantic,  the  glassy  zones  were 


Fig.  5. — Glassy  streaks  showing  the  centres  of  ascending  and  descending 
columns  of  air  in  the  Bay  of  Antibes,  Alpes  Maritimes. 

from  8  to  15  miles  apart,  I  often  found  them  not  more 
than  500  feet  apart  in  the  bays  of  the  Mediterranean. 
This  was  most  noticeable  at  Antibes  (Fig.  5),  very  good 
photographs  of  which  I  obtained.  It  will  be  observed 
that  the  whole  surface  of  the  water  is  streaked  like  a 
block  of  marble. 

At  Nice  and  Monte  Carlo  this  phenomena  was  also  very 
marked.  On  one  occasion,  while  making  observations 
from  the  highest  part  of  the  promontory  of  Monaco  on 
a  perfectly  calm  day,  I  noticed  that  the  whole  of  the  sea 
presented  this  peculiar  effect  as  far  as  the  eye  could  reach, 

2 


18  ARTIFICIAL    AND    NATURAL    FLIGHT. 

and  that  the  lines  which  marked  the  descending  air  were 
never  more  than  1,000  feet  from  those  which  marked  the 
centre  of  the  ascending  column.  At  about  three  o'clock 
one  afternoon,  a  large  black  steamer  passed  along  the  coast 
in  a  perfectly  straight  line,  and  its  wake  was  at  once 
marked  by  a  glassy  line,  which  indicated  the  centre  of  an 
ascending  column.  This  line  remained  almost  straight  for 
two  hours,  when  finally  it  became  crooked  and  broken. 
The  heat  of  the  steamer  had  been  sufficient  to  determine 
this  upward  current  of  air. 

In  1893  I  spent  two  weeks  in  the  Mediterranean,  going 
and  returning  by  a  slow  steamer  from  Marseilles  to  Con- 


.  \ 


b  c 


Fig.  6. — Air  currents  observed  in  the  Mediterranean,  ascending  currents 
at  a,  a,  a,  and  descending  currents  at  b,  b,  b. 

stantinople,  and  I  had  many  opportunities  of  observing 
the  peculiar  phenomena  to  which  I  have  referred.  The 
steamer  passed  over  thousands  of  square  miles  of  calm 
sea,  the  surface  being  only  disturbed  by  large  patches  of 
small  ripples  (Fig.  6),  sep  irated  from  each  other  by  glassy 
streaks,  which,  however,  were  not  straight  as  on  the 
Atlantic,  and  I  found  that  in  no  case  was  the  wind 
blowing  in  the  same  direction  on  both  sides  of  these 
streaks,  every  one  of  which  indicated  the  centre  of  an 
ascending  or  a  descending  column  of  air.  If  we  should 
investigate  these  phenomena  in  what  might  be  called  a 
dead  calm,  we  should  find  that  the  air  was  rising  very 


AIR    CURRENTS    AND    THE    FLIGHT    OF    BIRDS.  19 

nearly  straight  up  over  the  centres  of  some  of  these 
streaks  and  descending  in  a  vertical  line  over  the  centres 
of  others.  But,  as  a  matter  of  fact,  there  is  no  such  thing 
as  a  dead  calm.  The  movement  of  the  air  is  the  resultant 
of  more  than  one  force.  The  air  is  not  only  rising  in  some 
places  and  descending  in  others,  but  at  the  same  time,  the 
whole  mass  is  moving  forward  with  more  or  less  rapidity 
from  one  part  of  the  earth  to  another,  so  we  must  consider 
that,  instead  of  the  air  ascending  directly  from  the  rela- 
tively hot  surface  of  the  earth  and  descending  vertically 
in  other  places,  in  reality  the  whole  mass  of  rotating  air  is 
moving  horizontally  at  the  same  time. 

Suppose  that  the  local  influence  which  causes  the  up  and 
down  motion  of  the  air  should  be  sufficiently  great  to 
cause  the  air  to  rise  at  the  rate  of  2  miles  an  hour,  and 
that  the  wind  at  the  same  time  should  be  blowing  at  the 
rate  of  10  miles  an  hour,  the  motion  of  the  air  would  then 
be  the  resultant  of  these  two  velocities.  In  other  words, 
it  would  be  blowing  up  an  incline  of  1  in  5.  Suppose, 
now,  that  a  bird  should  be  able  to  so  adjust  its  wings 
that  it  advanced  5  miles  in  falling  1  mile  through  a 
perfectly  calm  atmosphere,  it  would  then  be  able  to 
sustain  itself  in  an  inclined  wind,  such  as  I  have 
described,  without  any  movement  at  all  of  its  wings. 
If  it  were  possible  to  adjust  its  wings  in  such  a  manner 
that  it  could  advance  6  miles  by  falling  through  1  mile 
of  air,  it  would  then  be  able  to  rise  as  relates  to  the  earth 
while  in  reality  falling  as  relates  to  the  surrounding  air. 

In  conducting  a  series  of  experiments  with  artillery  and 
small  guns  on  a  large  and  level  plain  just  out  of  Madrid, 
I  often  observed  the  same  phenomena,  as  relates  to  the 
wind,  that  I  have  already  spoken  of  as  having  observed 
at  sea,  except  that  the  lines  marking  the  centre  of  an 
ascending  or  a  descending  column  of  air  were  not  so 
stationary  as  they  were  over  the  water.  It  was  not  an 
uncommon  thing,  when  adjusting  the  sights  of  a  gun  to 
fire  at  a  target  at  a  very  long  range,  making  due  allow- 
ances for  the  wind,  to  have  the  wind  change  and  blow  in 
the  opposite  direction  before  the  word  of  command  was 
given  to  fire.  While  conducting  these  experiments,  I  often 
noticed  the  flight  of  eagles.  On  one  occasion  a  pair  of 
eagles  came  into  sight  on  one  side  of  the  plain,  passed 
directly  over  our  hea'is,  and  disappeared  on  the  opposite 
side.  They  were  apparently  always  at  the  same  height 


20  ARTIFICIAL    AND    NATURAL    FLIGHT. 

from  the  earth,  and  in  soaring  completely  across  the  plain 
they  never  once  moved  their  wings.  These  phenomena,  I 
think,  can  only  be  accounted  for  on  the  hypothesis  that  these 
birds  were  able  to  feel  out  with  their  wings  an  ascending 
column  of  air,  that  the  centre  of  this  column  of  air  was 
approximately  a  straight  line  running  completely  across 
the  plain,  that  they  found  upward  movement  more  than 
sufficient  to  sustain  their  weight  in  the  air,  and  that, 
whereas,  as  relates  to  the  earth,  they  were  not  falling  at 
all,  they  were  in  reality  falling  some  4  or  5  miles  an  hour 
in  the  air  which  supported  them. 

Again,  at  Cadiz  in  Spain,  when  the  wind  was  blowing 
in  strongly  from  the  sea,  I  observed  that  the  sea-gulls 
always  took  advantage  of  an  ascending  column  of  air. 
As  the  wind  rose  to  pass  over  the  fortifications,  the  gulls 
selected  a  place  where  they  would  glide  on  the  ascending 
current  of  air,  keeping  themselves  always  approximately 
in  the  same  place  without  any  apparent  exertion.  When, 
however,  they  left  this  ascending  column,  it  was  necessary 
for  them  to  work  their  wings  with  great  vigour  until  they 
again  found  the  proper  place  to  encounter  a  favourable 
current. 

I  have  often  noticed  that  gulls  are  able  to  follow  a  ship 
without  any  apparent  exertion ;  they  simply  balance  them- 
selves on  an  ascending  column  of  air,  where  they  seem  to 
be  quite  as  much  at  ease  as  they  would  have  been  roosting 
on  a  solid  support.  If,  however,  they  are  driven  out  of 
this  position,  they  generally  commence  at  once  to  work 
their  passage.  If  anything  is  thrown  overboard  which  is 
too  heavy  for  them  to  lift,  the  ship  soon  leaves  them 
behind,  and  in  order  to  catch  up  with  it  again  they  move 
their  wings  very  much  as  other  birds  do ;  but  when  once 
established  in  the  ascending  column  of  air,  they  manage 
to  keep  up  with  the  ship  by  doing  little  or  no  work.  In 
a  calm  or  head  wind  we  find  them  directly  aft  of  the 
ship;  if  the  wind  is  from  the  port  side  they  may  always 
be  found  on  the  starboard  quarter,  and  vice  versa. 

One  Sunday  morning,  while  living  at  Kensington,  I 
noticed  some  very  curious  atmospheric  effects.  The 
weather  had  been  intensely  cold  for  about  a  week,  when 
suddenly  the  atmosphere  became  warm  and  very  humid. 
The  earth  being  much  colder  than  the  atmosphere,  water 
was  condensing  on  everything  that  it  touched.  I  went 
to  the  bridge  over  the  Serpentine  in  Hyde  Park,  and  was 


AIR    CURRENTS    AND    THE    FLIGHT    OF    BIRDS.  21 

not  disappointed  in  finding  a  large  number  of  sea-gulls 
waiting  about  the  bridge  to  be  fed.  On  all  ordinary 
occasions  these  birds  manage  to  move  about  with  the 
expenditure  of  very  little  energy,  but  on  this  occasion 
every  one  of  them,  without  a  single  exception,  no  matter 
in  what  position  he  might  be,  was  working  his  passage 
like  any  other  bird,  just  as  I  had  expected.  It  is  'only 
on  very  rare  occasions  that  the  surface  of  the  earth  is 
sufficiently  cold  as  relates  to  the  atmosphere  to  prevent 
all  upward  currents  of  air. 

Everyone  who  has  passed  a  winter  on  the  northern 
shores  of  the  Mediterranean  must  have  observed  the  cold 
wind  which  is  generally  called  the  mistral.  One  may  be 
out  driving,  the  sun  may  be  shining  brightly,  and  the  air 
warm  and  balmy,  when  suddenly,  without  any  apparent 
cause,  one  finds  himself  in  a  cold  descending  wind.  This 
is  the  much-dreaded  mistral,  and  if  at  sea  it  would  be 
marked  by  a  glassy  line  on  the  surface  of  the  water. 
On  land,  however,  there  is  nothing  to  render  its  presence 
visible.  The  ascending  column  of  air  is,  of  course,  always 
very  much  warmer  than  the  descending  column,  and  this 
is  taking  place  in  a  greater  or  lesser  degree  everywhere 
and  at  all  times.  A  decided  upward  trend  of  air  is  often 
encountered  by  those  who  are  experimenting  with  kites, 
the  kite  often  mounting  higher  than  can  be  accounted  for 
on  the  hypothesis  that  the  wind  is  moving  in  a  horizontal 
direction.  I  have  heard  this  discussed  at  considerable 
length.  When  a  kite  is  flown  in  an  upward  current,  it 
behaves  in  many  respects  like  a  soaring  bird. 

From  the  foregoing,  I  think,  we  may  safely  draw  the 
following  conclusions : — 

First,  that  there  is  a  constant  interchange  of  air  taking 
place,  the  cold  air  descending,  spreading  itself  out  over 
the  surface  of  the  earth,  becoming  warm,  and  ascending 
in  other  places. 

Second,  that  the  centres  of  the  two  columns  are  generally 
separated  from  each  other  by  a  distance  which  may  be  from 
500  feet  to  20  miles. 

Third,  that  the  centres  of  greatest  action  are  not  in 
spots,  but  in  lines  which  may  be  approximately  straight, 
but  sometimes  abound  in  many  sinuosities. 

Fourth,  that  this  action  is  constantly  taking  place  over 
both  the  sea  and  the  land ;  that  the  soaring  of  birds,  the 
phenomenon  which  has  heretofore  been  so  little  under- 


22  ARTIFICIAL    AND    NATURAL    FLIGHT. 

stood,  may  be  accounted  for  on  the  hypothesis  that  the 
bird  seeks  out  an  ascending  column  of  air,  and  while 
sustaining  itself  at  the  same  height  in  the  air,  without 
any  muscular  exertion,  it  is  in  reality  falling  at  a  con- 
siderable velocity  through  the  air  that  surrounds  it. 

It  has  been  supposed  by  some  scientists  that  birds  may 
take  advantage  of  some  vibratory  or  rolling  action  of  the 
air.  I  find,  however,  from  careful  observation  and  experi- 
ment, that  the  motion  of  the  wind  is  comparatively  steady, 
and  that  the  short  vibratory  or  rolling  action  is  alwrays 
very  near  to  the  earth  and  is  produced  by  the  air  flowing 
over  hills,  high  buildings,  trees,  etc. 

Tools  and  instruments  used  by  mechanicians  are  very 
often  made  of  the  material  most  used  in  their  profession ; 
for  instance,  a  blacksmith's  tools  are  generally  of  iron,  a 
carpenter's  tools  largely  of  wood,  and  a  glass-blower  uses 
many  things  made  of  glass,  and  so  on.  Mathematicians 
are  no  exception  to  this  general  rule,  and  seem  to  imagine 
that  everything  can  be  accomplished  by  pure  mathematical 
formulae. 

It  appears  that  Prof.  Langley  was  at  times  considerably 
puzzled  by  the  extraordinary  behaviour  of  birds,  and  was 
led  to  believe  that  they  took  advantage  of  some  vibratory 
or  oscillating  movement  of  the  air ;  he  called  it  "  the 
internal  work  of  the  air."  I  have  been  very  much 
amused  in  a  recent  mathematical  work  that  I  have  read, 
in  which  the  writer  seeks  to  solve  all  questions  by  pure 
mathematics.  In  this  case,  notwithstanding  that  all  of 
the  factors  are  unknown  and  unknowable,  still,  with  the 
use  of  about  two  pages  of  closely  written  algebraic  formulae, 
he  appears  to  have  solved  the  whole  question.  Just  how 
he  arrived  at  it,  however,  is  more  than  I  am  able  to  under- 
stand. 

If  a  kite  is  flown  only  a  few  feet  above  the  ground,  it 
will  be  found  that  the  current  of  air  is  very  unsteady.  If 
it  is  allowed  to  mount  to  500  feet  the  unsteadiness  nearly 
all  disappears,  while  if  it  is  allowed  to  mount  further  to 
a  height  of  1,500  or  2,000  feet,  the  pull  on  the  cord  is 
almost  constant,  and,  if  the  kite  is  well  made,  it  remains 
practically  stationary  in  the  air. 

I  have  often  noticed  in  high  winds  that  light  and  fleecy 
clouds  come  into  view,  say,  about  2,000  feet  above  the 
surface  of  the  earth,  and  pass  rapidly  and  steadily  by 
preserving  their  shape  completely.  This  would  certainly 


AIR    CURRENTS    AND    THE    FLIGHT    OF    BIRDS.  23 

indicate  that  there  is  no  rapid  local  disturbance  in  the 
air  in  their  immediate  vicinity,  but  that  the  whole  mass 
of  air  in  which  these  clouds  are  formed  is  practically 
travelling  in  the  same  direction  and  at  the  same  velocity. 
Numerous  aeronauts  have  also  testified  that,  no  matter 
how  hard  the  wind  may  be  blowing,  the  balloon  is  always 
practically  in  a  dead  calm,  and  if  a  piece  of  gold-leaf  is 
thrown  overboard,  even  in  a  gale,  the  gold-leaf  and  the 
balloon  never  part  company  in  a  horizontal  direction, 
though  they  may  in  a  vertical  direction. 

Birds  may  be  divided  into  two  classes.  First,  the 
soaring  birds,  which  practically  live  upon  the  wing,  and, 
by  some  very  delicate  sense  of  touch,  are  able  to  feel 
the  exact  condition  of  the  air.  Many  fish  which  live 
near  the  top  of  the  water  are  greatly  distressed  by 
sinking  too  deeply,  while  others  which  live  at  great 
depths  are  almost  instantly  killed  by  being  raised  to 
the  surface.  The  swim -bladder  of  a  fish  is  in  reality  a 
delicate  barometer  provided  with  sensitive  nerves  which 
enable  the  fish  to  feel  whether  it  is  sinking  or  rising  in 
the  water.  With  the  surface  fish,  if  the  pressure  becomes 
too  great,  it  involuntarily  exerts  itself  to  rise  nearer  the 
surface  and  so  diminish  the  pressure,  and  I  have  no  doubt 
that  the  air  cells,  which  are  known  to  be  very  numerous 
and  to  abound  throughout  the  bodies  of  birds,  are  so 
sensitive  as  to  enable  soaring  birds  to  know  at  once 
whether  they  are  in  an  ascending  or  a  descending  column 
of  air. 

The  other  class  of  birds  consists  of  those  which  only 
employ  their  wings  occasionally  for  the  purpose  of  taking 
them  rapidly  from  one  place  to  another.  Such  birds  do 
not  expend  their  power  so  economically  as  the  soaring 
birds.  They  do  not  pass  much  of  their  time  in  the  air, 
but  what  time  they  are  on  the  wing  they  put  forth  an 
immense  amount  of  power  and  fly  very  rapidly,  generally 
in  a  straight  line,  taking  no  advantage  of  air  currents. 
Partridges,  pheasants,  wild  ducks,  geese,  and  some  birds  of 
passage  may  be  taken  as  types  of  this  kind.  This  class 
of  birds  has  relatively  small  wings,  and  carries  about  two 
and  a  half  times  as  much  weight  per  square  foot  of  surface 
as  soaring  birds  do. 

We  shall  never  be  able  to  imitate  the  flight  of  the  soaring 
birds.  We  cannot  hope  to  make  a  sensitive  apparatus 
that  will  work  quick  enough  to  take  advantage  of  the 


•24 


ARTIFICIAL    AND    NATURAL    FLIGHT. 


rising  currents  of  air,  and  he  who  seeks  to  fly  has  this 
problem  to  deal  with.  A  successful  flying  machine,  moving 
at  a  high  velocity,  is  likely  at  any  time  to  encounter  down- 
ward currents  of  air,  which  will  greatly  interfere  with  its 
action.  Therefore  "flying  machines  must,  in  the  very  nature 
of  things,  be  provided  with  sufficient  power  to  propel  them 
through  various  currents  of  air,  after  the  manner  of  ducks, 
partridges,  pheasants,  etc. 


Common  Name. 

Sq.  Ft.  per  Lb. 

Lbs.perSq.Ft. 

Corresponding 
Speed  for  a  Plane 
at  3°  in  Miles 
per  Hour. 

Bat  

•64 

0-131 

15-9 

Swallow,  . 

3-62 

0-276 

23-1 

Lark, 

3-06 

0-327 

25-1 

Sparrow  hawk, 
Sparrow,  . 

3-00 
2-42 

0-333 
0-414 

25-3 

28-2 

Gull, 

2-35 

0-426 

28-6 

Owl, 

2-26 

0-443 

29-2 

Crane,       . 

2-02 

0-495 

30-9 

Rook, 

1-74 

0-575 

33-3 

Plover,      . 

1-38 

0-725 

37-4 

Balbuzzard, 

1-26 

0-795 

39-2 

Egyptian  vulture,     . 

1-18 

0-848 

40-4 

Duck, 

0-864 

1-158 

44-2 

Grey  pelican,    . 

0-732 

1  -365 

51-3 

Wild  goose,       . 

0-586 

1-708 

57-4 

Turkey,    . 

0-523 

1-910 

60-6 

Duck  (female),  . 

0-498 

2-008 

62-2 

,,     (male),     . 

0-439 

2-280 

66-2 

CHAPTER  III. 
FLYING     OP     KITES. 

IT  was  said  of  Benjamin  Franklin  that  when  he  wished  to 
fly  a  kite  in  order  to  ascertain  if  lightning  could  be  drawn 
down  from  the  clouds,  he  managed  to  have  a  boy  with  him 
in  order  to  avoid  ridicule.  It  was  considered  too  frivolous 
in  those  days  for  grown-up  men  to  amuse  themselves  with 
kites,  and  a  good  many  besides  Benjamin  Franklin  have 
feared  to  face  the  ridicule  that  was  inevitable  if  they 
took  up  or  even  discussed  the  question  of  artificial  flight. 
Nineteen  years  ago,  when  I  commenced  my  own  experi- 
ments, I  was  told  that  my  reputation  would  be  greatly 
injured,  that  mankind  looked  upon  artificial  flight  as  an 
ignis-fatuus,  and  that  anyone  who  experimented  in  that 
direction  was  placed  in  the  same  category  as  those  who 
sought  to  make  perpetual-motion  machines  or  to  find  the 
philosopher's  stone.  Although  I  had  little  fear  of  ridicule, 
still  I  kept  things  as  quiet  as  I  could  for  a  considerable 
time,  and  I  had  been  working  fully  six  months  before 
anyone  ascertained  what  I  was  doing.  When,  however, 
it  became  known  that  I  was  experimenting  with  a  view 
of  building  a  flying  machine,  the  public  seemed  to  think 
that  I  was  making  honest  and  praiseworthy  scientific 
investigations ;  true,  I  might  not  succeed,  still  it  was  said 
that  I  would  accomplish  something,  and  find  out  some  of 
the  laws  relating  to  the  subject.  No  one  ridiculed  my 
work  except  two  individuals,  and  both  of  these  were  men 
whom  I  had  greatly  benefited.  As  is  often  the  case,  those 
whom  you  find  in  difficulties  and  place  'on  their  feet  seek 
to  do  you  some  injury  as  compensation  for  the  benefits 
they  have  received. 

At  the  present  time  it  is  not  necessary  for  any  man  to 
take  a  small  boy  with  him  as  a  species  of  lightning-rod  to 
ward  off  ridicule  when  he  flies  a  kite.  1  have  been  one  of 
a  committee  on  kite-flying  at  which  some  of  the  most 
learned  and  serious  men  in  England  were  my  colleagues 
in  investigating  the  subject.  The  behaviour  of  kites  is 
certainly  very  puzzling  to  those  who  do  not  thoroughly 


26  ARTIFICIAL    AND    NATURAL    FLIGHT. 

understand  the  subject.  A  kite  may  be  made  with  the 
greatest  degree  of  perfection,  and  placed  in  the  hands  of 
one  of  considerable  experience ;  nevertheless,  it  may  behave 
very  badly,  diving  suddenly  to  the  ground  without  any 
apparent  cause.  Then,  again,  this  same  kite  will  sometimes 
steadily  mount  in  the  air  until  it  reaches  a  height  difficult 
to  account  for.  If  the  surface  of  the  earth  should  be 
perfectly  smooth,  and  the  wind  should  always  blow  in  a 
horizontal  direction,  kites  would  not  show  these  eccentric 
peculiarities,  but,  as  a  matter  of  fact,  the  air  seldom  moves 
in  a  horizontal  direction;  it  is  always  influenced  by  the 
heat  of  the  surface  of  the  earth.  Heated  air  is  continually 
ascending  in  some  places  only  to  be  cooled  and  to  descend 
in  other  places.  If  one  is  attempting  to  fly  a  kite  where 
the  air  is  moving  downwards,  he  will  find  it  an  extremely 
difficult  matter,  whereas,  if  he  is  fortunate  enough  to  strike 
a  current  of  air  which  is  rising,  the  kite  will  mount  much 
higher  in  the  air  than  can  be  accounted  for,  except  we 
admit  of  the  existence  of  these  upward  draughts  of  air. 
On  one  occasion  many  years  ago,  I  was  present  when  a 
bonded  warehouse  in  New  York  containing  10,000  barrels 
of  alcohol  was  burnt.  It  was  nine  o'clock  at  night,  and 
1  walked  completely  around  the  fire,  arid  found  things 
just  as  I  had  expected.  The  wind  was  blowing  a  perfect 
hurricane  through  every  street  in  the  direction  of  the  fire, 
although  it  was  a  dead  calm  everywhere  else ;  the  flames 
mounted  straight  in  the  air  to  an  enormons  height,  and 
took  with  them  a  large  amount  of  burning  wood.  When 
I  was  fully  500  feet  from  the  fire,  a  piece  of  partly  burnt 
1-inch  board,  about  8  inches  wide  and  4  feet  long,  fell 
through  the  air  and  landed  very  near  me,  sending  sparks 
in  every  direction.  This  board  had  evidently  been  taken 
up  to  a  great  height  by  the  tremendous  uprush  of  air 
caused  by  the  burning  alcohol.  It  is  very  evident  that 
a  kite  made  of  boiler  iron  could  have  been  successfully 
flown  under  these  conditions  providing  that  it  could  have 
been  brought  into  the  right  position. 

The  sketch  (Fig.  7)  shows  a  device  consisting  of  a  spirit 
lamp  and  a  box  of  ice.  The  lamp  heats  the  metallic  plate, 
expands  the  air  which  rises  and  is  cooled  by  convection 
on  coming  in  contact  with  the  top  plate,  and  descends  as 
shown.  However,  a  fire  is  not  necessary  to  accomplish  this 
result ;  it  as  taking  place  all  over  the  earth,  all  the  time. 
A  great  number  of  plants  depend  upon  a  rising  current  of 


FLYING    OF    KITES. 


27 


air  to  transport  their  seeds  to  distant  places.  Seeds  of  the 
thistle  and  dandelion  variety  are  sometimes  able  to  travel 
hundreds  of  miles,  to  the  great  vexation  of  farmers ;  and 
there  is  a  certain  class  of  small  spider  known  as  "Balloon 
Spiders  "  which  also  depend  upon  a  rising  current  of  air  to 
carry  them  from  the  place  of  their  birth  to  some  distant 


Fig.  7. — The  circulation  of  air  produced  by  a  difference  in  temperature. 

part  where  they,  of  course,  hope  to  start  a  colony.  When 
I  was  a  boy  of  eight,  I  noticed  small  spiders  webbing  down 
from  the  sky.  I  was  greatly  puzzled  ;  it  appeared  to  me 
that  they  had  attached  their  web  to  some  stationary  object 
high  in  the  air  and  were  spinning  a  web  in  order  to  lower 
themselves  to  the  earth.  What  could  that  stationary  object 
be  ?  As  the  sky  was  clear,  I  was  quite  unable  to  understand 


28  ARTIFICIAL   AND    NATURAL    FLIGHT. 

this  phenomenon,  but  afterwards  I  learned  from  scientific 
books  that  there  was  a  class  of  spiders  that  managed  to 
rise  high  in  the  air  by  the  aid  of  the  wind.  It  appears 
that  they  climb  a  high  tree  until  they  have  reached  the 
uppermost  extremity  and  then,  from  a  leaf  or  twig  that 
projects  into  the  air,  they  wait  for  an  ascending  current  of 
air.  Although  the  spider  is  exceedingly  small — the  size  of 
a  pin's  head — it  has  about  200  spinnerets,  its  ordinary  web 
being  formed  of  no  less  than  that  number  of  extremely  fine 
threads.  These  are  spun  out  singly  into  the  air  until  an 
almost  invisible  mass  of  fine  webs  interlacing  each  other  in 
all  directions  and  forming  an  approximately  cylindrical 
network  about  half  an  inch  in  diameter  and  18  inches 
long  is  produced.  .  Whenever  an  upward  draft  of  air 
approximately  vertical  occurs,  it  takes  this  weightless 
tangle  of  fine  webs  with  it,  and  so  soon  as  the  spider  finds 
there  is  sufficient  pull  to  lift  its  weight,  it  lets  go  and 
ascends  with  the  air.  When  the  Nulli  Secundus  ascended 
at  Farnborough  and  landed  at  the  Crystal  Palace,  Mr. 
Cody,  who  was  on  board,  reported  what  he  supposed  to  be 
a  very  curious  and  unaccountable  phenomenon.  The 
balloon  was  covered  with  many  thousands  of  minute 
spiders  that  it  had  picked  up  in  the  air  on  the  voyage. 
Certainly  this  of  itself  is  very  strong  evidence  of  the 
existence  of  these  ascending  currents  of  air. 

When  in  Boston  about  fifteen  years  ago,  I  went  to  Blue 
Hill  to  witness  the  remarkable  kite  flying  which  was 
taking  place  at  that  time.  The  kites  experimented  with 
were  of  the  Hargrave  type,  and  of  enormous  dimensions. 
A  steel  wire  and  windlass  worked  by  a  steam  engine  was 
employed.  I  was  told  that  on  certain  occasions  the  kites 
mounted  extremely  high,  much  higher  than  they  were  able 
to  account  for ;  but  on  this  particular  occasion,  although 
they  let  out  a  great  amount  of  wire,  the  kite  did  not  mount 
very  high.  I  have  heard  much  discussion  first  and  last 
regarding  the  flight  of  kites,  and  I  think  it  is  generally 
admitted  that  they  do  sometimes  rise  upwards  and  con- 
tinue moving  to  the  windward  until  they  pass  directly 
over  the  spot  where  they  are  attached  to  the  earth.  It 
was  not,  however,  till  about  three  years  ago  that  I 
witnessed  this  phenomenon  myself.  Mr.  Cody,  who  is  the 
inventor  of  a  very  good  kite,  had  been  flying  kites  at  the 
Crystal  Palace  for  some  months,  and  on  one  occasion  I  saw 
his  kite  rise,  pass  to  the  windward  and  directly  over  our 


FLYING    OF    KITES. 


29 


heads.  I  took  hold  of  the  cord  with  both  hands,  and  was 
somewhat  surprised  to  find  what  the  lifting  effect  was. 
The  kite  was,  however,  of  large  dimensions,  but  by  no 
means  so  large  as  Mr.  Cody's  "  man-lifting  kites."  In  the 


drawing  (Fig.  8)  I  have  shown,  at  a,  the  action  of  a  kite  in 
a  horizontal  wind,  lines  e,  e,  showing  the  direction  of  the 
wind.  A  good  kite  will  easily  mount  45°,  the  angle  shown, 
but  on  the  occasion  just  mentioned,  the  sun  had  been 
shining  brightly  into  the  valley  where  the  experiments 


30  ARTIFICIAL    AND    NATURAL    FLIGHT. 

took  place,  and  an  upward  current  of  air  had  been  deter- 
mined. The  cooler  air  was,  of  course,  rushing  in  from  each 
side  and  mounting  in  about  the  centre  of  the  valley,  and 
Mr.  Cody's  kite,  instead  of  flying  in  a  horizontal  wind, 
soon  reached  a  point  where  the  wind  was  ascending  at 
an  angle,  as  shown  at  /,  /.  The  kite  would  therefore 
mount  until  at  6,  where  it  presented  the  same  angle 
to  the  wind  as  with  the  horizontal  wind  at  a,  and 
if  it  should  be  made  to  fly  at  a  higher  angle,  it 
might  pass  over  to  the  position  shown  at  c.  But 
it  must  not  be  imagined  that  this  phenomenon  can  be 
witnessed  every  day  in  the  year.  It  is  only  on  rare 
occasions  that  one  is  fortunate  enough  to  find  a  wind 
which  is  blowing  at  a  sufficiently  sharp  upward  trend  to 
cause  a  kite  to  pass  to  the  windward  over  the  point  of 
support.  Neither  must  it  be  supposed  that  this  favourable 
condition  of  things  is  of  long  duration.  As  the  centre  of 
the  upward  current  is  constantly  moving,  it  is  certain  that 
very  soon  it  will  move  away  from  the  point  from  which 
the  kite  is  being  flown.  What  is  true  of  kites  is  also  true 
of  flying  machines.  It  is  very  difficult  indeed  to  make  a 
kite  mount  providing  that  it  is  in  a  descending  current  of 
air,  and  one  is  just  as  likely  to  find  a  descending  current 
as  any  other.  Flying  machines  will,  therefore,  have  to  be 
made  with  a  considerable  amount  of  reserve  energy,  so  as 
to  be  able  to  put  on  a  spurt  when  they  encounter  an 
adverse  current.  If  a  machine  is  made  that  is  able  to 
maintain  itself  in  the  air  for  any  considerable  length  of 
time,  it  will  not  be  a  very  difficult  task  to  know  when  a 
current  of  air  of  this  kind  is  encountered,  because,  if  the 
engine  is  working  up  to  speed,  and  everything  is  in  perfect 
order,  and  still  the  machine  is  falling,  it  is  very  certain 
that  an  unfavourable  current  has  been  encountered,  and 
efforts  should  be  made  to  get  out  of  it  as  soon  as  possible. 
Then,  again,  if  the  machine  has  an  abnormal  tendency  to 
rise  without  any  increase  in  the  number  of  rotations  made 
by  the  screws,  the  aeronaut  may  be  certain  that  he  has 
encountered  an  upward  and  favourable  current  of  air 
which,  unfortunately,  will  not  last.  It  should,  however, 
be  borne  in  mind  that,  while  the  width  of  the  upward 
current  is  not  very  great,  nevertheless,  it  may  extend  in  a 
practically  straight  line  for  many  miles. 


31 


CHAPTER  IV. 
PRINCIPALLY   RELATING   TO    SCREWS. 

Iv  1887  I  was  approached  by  several  wealthy  gentlemen 
who  asked  me  if  I  thought  it  was  possible  to  make  a 
flying  machine.  I  said,  "  certainly ;  the  domestic  goose 
is  able  to  fly  and  why  should  not  man  be  able  to  do  as 
well  as  a  goose?"  They  then  asked  me  what  it  would 
cost  and  how  long  it  would  take,  and,  without  a  moment's 
hesitation,  I  said  it  would  require  my  undivided  attention 
for  five  years  and  might  cost  £100,000.  A  great  deal  of 
experimenting  would  be  necessary ;  the  first  three  years 
would  be  devoted  to  developing  an  internal  combustion 
engine  of  the  Brayton  or  Otto  type,  and  the  next  two 
years  to  experimenting  with  aeroplanes  and  screws  and 
building  a  machine.  Even  at  that  time  I  had  a  clear  idea 
of  the  system  that  would  be  the  best.  However,  nothing 
was  then  done,  but  in  1889  I  employed  for  the  purpose 
two  very  skilful  American  mechanics,  and  put  them  to 
work  at  Baldwyn's  Park,  Kent.  At  that  time  the 
petroleum  motor  had  not  been  reduced  to  its  present 
degree  of  efficiency  and  lightness;  it  was  not  suitable 
for  a  flying  machine,  and  1  saw  that  it  would  require 
a  lot  of  experimental  work  in  order  to  develop  it.  After 
taking  into  consideration  all  the  facts  of  the  case,  I  decided 
to  use  a  steam  engine.  Had  I  been  able  to  obtain  the 
light  and  efficient  motors  which  have  been  recently 
developed,  thanks  to  the  builders  of  racing  cars,  I 
should  not  have  had  to  experiment  at  all  with  engines 
and  boilers,  as  I  could  have  obtained  the  necessary  motors 
at  once.  As  it  was,  I  was  obliged  to  content  myself  with 
the  steam  engine. 

I  found  that  there  was  a  great  deal  of  misunderstanding 
regarding  the  action  of  aeroplanes,  and  also  of  screws 
working  in  the  air.  I  procured  all  the  literature  avail- 
able on  the  subject,  both  English  and  French,  and 
attempted  to  make  a  thorough  study  of  the  question; 
but  I  was  not  satisfied,  on  account  ot  the  wide  difference 
in  the  views  of  the  writers  and  the  conflicting  formulae 
that  were  employed.  I  therefore  decided  to  make  experi- 


32  ARTIFICIAL    AND    NATURAL    FLIGHT. 

ments  myself,  and  to  ascertain  what  could  be  done  without 
the  use  of  anybody's  formula.     Although  this  was  nearly 


Fig.  9. — Group  of  screws  and  other  objects  used  in  my  experiments. 

twenty  years  ago,  I  find  that  there  is  still  a  great  deal  of 
discussion  regarding  the  action  of  aeroplanes  and  screws, 


Fig.   10. — Some  of  the  principal  screws  experimented  with — h,  a  screw 
with  very  thick  blades,  and  g,  a  screw  made  after  a  French  model. 

in  which  the  majority  taking  part  in  the  discussion  are  in 
the  wrong.  However,  several  good  works  on  the  subject 
have  recently  been  published. 


PRINCIPALLY    RELATING   TO    SCREWS.  33 

Having  designed  and  put  my  boiler  and  engine  in  hand, 
I  commenced  a  series  of  experiments  for  the  purpose  of 
ascertaining  the  efficiency  of  screw  propellers  working 
in  the  air,  and  the  form  and  size  that  would  be  best  for 
my  proposed  machine.  The  illustration  Fig.  9  shows  a 
photographic  group  of  the  screws  and  other  objects  with 
which  I  experimented.  Fig.  10  shows  some  of  the  leading 
types  which,  as  will  be  seen,  have  blades  of  different  shape, 
pitch,  and  size.  Fig.  11  shows  three  of  the  best  screws 
employed.  It  will  be  observed  that  one  has  uniform  pitch, 
another  increasing  pitch,  and  the  third  compound  increasing 
pitch.  In  order  to  test  the  efficiency  of  my  screws  I  made 
the  apparatus  shown  in  Fig.  12.  The  power  for  running 
the  screw  was  transmitted  by  means  of  a  belt  to  the 
straight  cylindrical  pulley  c,  c.  Shaft  b,  b  was  of  steel, 
rather  small  in  diameter,  and  ran  smoothly,  and  practically 


Fig.  11. — The  three  best  screws.  The  screw  on  the  right  has  a  uniform 
pitch  throughout,  the  middle  screw  has  increasing  pitch,  and  the  left 
screw  compound  increasing  pitch. 

without  friction,  through  the  two  bearings  d,  d.  When 
the  first  screw,  a,  a,  was  run  at  a  high  velocity,  the  axial 
thrust  pushed  the  shaft  6,  b  back  and  elongated  the  spiral 
spring  e.  The  degree  of  screw  thrust  was  indicated  in 
pounds  by  the  pointer  g.  The  power  was  transmitted 
through  a  very  accurate  and  sensitive  dynamometer,  so 
that  the  amount  consumed  could  be  easily  observed  by 
a  pointer  similar  to  the  one  employed  for  indicating  the 
screw  thrust.  A  tachometer  was  also  employed  to  observe 
the  number  of  turns  that  the  screw  was  making  in  a 
minute.  The  whole  apparatus  was  carefully  and  accurately 
made  and  worked  exceedingly  well.  I  was  thus  enabled, 
with  my  various  forms  of  screws  and  other  objects,  to 
make  very  accurate  measurements,  some  of  which  are 
exceedingly  interesting. 

In  many  of  the  treatises  and  books  of  that  time  it  was 

3 


PRINCIPALLY    RELATING   TO    SCREWS.  35 

stated  that  a  screw  propeller,  working  in  the  air,  was 
exceedingly  wasteful  of  energy  on  account  of  producing 
a  fan-blower  action.  Some  inventors  suggested  that  the 
screw  should  work  in  a  stationary  cylinder,  or,  better 
still,  that  the  whole  screw  should  be  encased  in  a  rotating 
cylinder,  to  prevent  this  outward  motion  of  the  air.  In 


Fig.  13. — Apparatus  for  testing  the  direction  of  air  currents  caused  by  a 
rapidly  rotating  screw.  Silken  threads  were  attached  to  the  wire  c,  c » 
which  indicated  clearly  the  direction  in  which  the  air  was  moving. 

order  to  ascertain  what  the  actual  facts  were,  I  attached 
a  large  number  of  red  silk  threads  to  a  brass  wire,  which 
I  placed  completely  around  my  screw  (see  Fig.  13).  Upon 
starting  up  I  found  that,  instead  of  the  air  being  blown 
out  at  the  periphery  of  the  screw,  it  was  in  reality  sucked 
in,  as  will  be  seen  in  the  illustration.  I  was  rather  sur- 


36  ARTIFICIAL    AND    NATURAL    FLIGHT. 

prised  to  see  how  sharp  a  line  of  demarkation  there  was 
between  the  air  that  was  moving  in  the  direction  of  the 
screw  and  the  air  that  was  moving  in  the  opposite 
direction.  The  screw  employed  in  these  experiments'  was 
18  inches  in  diameter  and  had  a  pitch  of  24  inches.  It 
was  evident,  however,  if  the  pitch  of  the  screw  was  coarse 
enough  that  there  would  be  a  fan-blower  action.  I  there- 
fore tried  screws  of  various  degrees  of  pitch,  and  found 
when  the  pitch  was  a  little  more  than  three  times  the 


Fig.  14. — This  drawing  shows  the  ends  of  screw  blades  in  which  a  is  a 
plain  screw;  6,  screw  with  increasing  pitch;  c,  screw  with  compound 
increasing  pitch ;  d,  end  of  screw  blade  45° ;  e,  screw  with  very  thick 
blade;  /,  blade  with  no  pitch  at  all;  g,  blade  which  gave  a  thrust  in 
the  direction  of  the  convex  side,  no  matter  in  which  direction  it  was 
revolved ;  h,  screw  said  to  have  been  used  in  the  French  Government 
experiments. 

diameter,  giving  to  the  outer  end  of  the  blade  an  angle 
of  45°,  that  a  fan -blower  action  was  produced — that  is, 
part  of  the  time  when  the  screw  was  running,  the  air 
would  alternate;  sometimes  it  would  pass  inwards  at  the 
periphery  and  sometimes  outwards.  The  change  of  direc- 
tion, however,  was  always  indicated  by  a  difference  in 
the  pitch  of  the  note  given  out,  and  also  by  the  thrust. 
In  Fig.  14  I  have  shown  the  extremities  of  the  blades  of 
some  of  the  different  forms  of  screws  experimented  with. 


PRINCIPALLY  RELATING  TO  SCREWS.  37 

in  which  a  shows  a  plain  screw,  the  front  side  being 
straight  and  of  equal  pitch  from  the  periphery  to  the 
hub;  6  is  a  screw  of  practically  the  same  pitch,  but 
slightly  curved  so  as  to  give  what  is  known  as  an 
increasing  pitch;  c  shows  the  extremity  of  a  screw  in 
which  the  curve  is  not  the  same  throughout — that  is,  it 
is  what  is  known  as  a  compound  increasing  pitch ;  d  is 
the  shape  of  the  screw  that  gave  the  angle  of  45°  above 
referred  to 

The  first  screw  experimented  with  was  a.  This  screw 
was  run  at  a  high  velocity — about  2,500  revolutions  per 
minute — until  a  screw  thrust  of  14  Ibs.  was  obtained,  and 
then  the  governor  of  the  engine  was  set  so  that  all  screws 
of  the  same  diameter  could  be  run  at  the  same  speed. 
Wishing  to  ascertain  the  efficiency  of  the  screw  and  how 
much  was  lost  in  skin  friction,  I  multiplied  the  thrust  in 
pounds  by  the  pitch  of  the  screw  in  feet  and  by  the 
number  of  turns  it  was  making  in  a  minute.  This,  of 
course,  gave  the  exact  number  of  foot-pounds  in  energy 
that  was  being  imparted  to  the  air.  I  was  somewhat 
surprised  to  find  that  it  corresponded  exactly  with  the 
readings  of  the  dynamometer.  I  thought  at  first  that 
I  must  have  made  some  mistake.  Again  I  went  very 
carefully  over  all  the  figures,  tested  everything,  and 
made  another  experiment  and  found,  even  if  I  changed 
the  number  of  revolutions,  that  the  readings  of  the 
dynamometer  were  always  exactly  the  same  as  the 
energy  imparted  to  the  air.  This  seemed  to  indicate 
that  the  screw  was  working  very  well  and  that  the  skin 
friction  must  be  very  small  indeed.  In  order  to  test  this, 
I  made  what  we  will  call,  for  the  moment,  a  screw  without 
any  pitch  at  all — that  is,  the  blades  were  of  wood  and  of 
the  exact  thickness  and  width  of  the  blades  of  the  screw  a, 
but  without  any  pitch  at  all.  The  extremity  of  the  blade 
is  shown  at  /.  I  placed  this  screw  on  my  machine  in  place 
of  a,  and  although  my  dynamometer  was  so  sensitive  that 
the  pointer  would  move  away  from  the  zero  pin  by  simply 
touching  the  tip  of  the  finger  to  the  shaft,  it  failed  to 
indicate,  and  thus  the  screw  appeared  to  consume  no  power 
at  all.  These  experiments  were  repeated  a  considerable 
number  of  times.  I  then  obtained  a  sheet  of  tin  the  same 
diameter  as  the  screws,  18  inches,  and  upon  running  it  at 
the  same  speed,  I  found  that  it  did  consume  a  measurable 
amount  of  power,  certainly  more  than  the  two  blades  /. 

136510 


38  ARTIFICIAL    AND    NATURAL    FLIGHT. 

This  no  doubt  was  due  to  the  uneven  surface  of  the  tin. 
Had  it  been  a  well-made  saw  blade  without  teeth,  perfectly 
smooth  and  true  on  both  sides,  it  probably  would  not  have 
required  power  enough  to  have  shown  on  the  dynamometer. 
However,  it  is  quite  possible  that  there  is  a  little  more 
skin  friction  with  a  polished  metallic  surface,  than  with  a 
piece  of  smooth  evenly  lacquered  wood.  The  screws  which 
I  employed  were  of  American  white  pine  such  as  used  by 
patternmakers.  This  wood  was  free  from  blemishes  of  all 
kind,  extremely  light,  uniform,  and  strong.  When  the 
screw  had  been  formed,  it  was  varnished  on  both  sides  with 
a  solution  of  hot  glue,  which  greatly  increased  the  strength 
of  the  wood  crosswise  of  the  grain.  When  this  glue  was 
thoroughly  dry,  the  wood  was  sand-papered  until  it  was  as 
smooth  as  glass ;  the  whole  thing  was  then  carefully  var- 
nished with  shellac,  rubbed  down  again  and  revarnished 
with  very  thin  shellac  something  like  lacquer.  In  this  way 
the  surface  of  the  screw  was  made  very  smooth.  The  screws, 
of  course,  were  made  with  a  great  degree  of  accuracy  and 
as  free  as  possible  from  any  unevenness.  Having  tested 
screw  a,  I  next  tested  screw  b.  I  found  with  the  same 
number  of  revolutions  per  minute  that  this  screw  produced 
more  thrust,  but  it  required  more  power  to  run  it,  and 
when  the  energy  imparted  to  the  air  was  compared  with 
the  readings  of  the  dynamometer,  it  was  found  that  it  did 
not  do  quite  so  well  as  a;  still  as  the  thrust  was  greater  and 
the  efficiency  only  slightly  less,  it  appeared  to  be  the  better 
screw.  Upon  trying  screw  c,  under  the  same  conditions, 
the  thrust  was  very  much  increased,  but  the  power 
required  was  also  increased  to  a  still  greater  degree,  show- 
ing that  this  form  was  not  so  favourable  as  either  a  or  b. 
All  the  screws  experimented  with  had  very  thin  blades, 
and  it  occurred  to  me  that  the  difference  between  a  and  b 
might  arise  from  the  fact  that,  when  a  was  running  at  a 
very  high  velocity,  the  working  side  instead  of  being  flat 
might  have  become  convex  to  a  slight  extent,  whereas  with 
b,  a  slight  bending  back  of  the  edges  of  the  blade  would 
still  leave  the  working  side  concave.  I  therefore  made 
the  screw  shown  at  e,  which  had  the  same  pitch  as  the 
other  three,  but  the  working  side  was  of  the  same  shape  as 
a.  Of  course  the  additional  thickness  of  the  blades  made 
it  impossible  to  give  an  easy  curve  to  the  back.  Curiously 
enough  I  found  that  e,  did  nearly  as  well  as  a,  and  quite  as 
well  as  b.  The  additional  thickness  did  not  interfere  to 


PRINCIPALLY    RELATING    TO    SCREWS. 


39 


any  appreciable  extent  with  its  efficiency.  I  then  made 
another  propeller,  shown  at  g,  which  was  of  the  same 
thickness  in  the  middle  as  e.  Upon  running  this,  I  found 
that  it  required  considerable  power,  and  no  matter  which 
way  it  was  run,  the  thrust  was  always  in  the  direction  of 
the  convex  side,  which  was  quite  the  reverse  from  what 
one  would  have  naturally  supposed. 

About  the  time  that  I  was  making  these  experiments, 
my  duties  called  me  to  Paris,  and  while  there  I  called  on 
my  old  friend  Gaston  Tissandier.  Through  his  influence  I 
was  permitted  to  see  some  models  of  the  screws  that  were 
alleged  to  have  been  used  by  Captain  Renard  in  his 
experiments  for  the  French  Government,  and  I  was  some- 
what surprised  to  find  the  form  of  the  blades,  the  same  as 


Fig.  15. — The  manner  of  building  up  the  large  screws. 

shown  at  h,  Fig.  14,  and  completely  without  any  twist. 
On  my  return  to  England,  I  made  a  screw  of  this  descrip- 
tion. It  is  also  shown  in  the  photographic  illustration, 
Fig  9.  Upon  testing  this  screw,  I  found  that  its  efficiency 
was  only  40  per  cent,  of  that  of  a — that  is,  the  energy  or 
acceleration  imparted  to  the  air  was  only  40  per  cent,  of 
the  readings  of  the  dynamometer.  It  then  occurred  to  me 
that  this  particular  form  of  screw  was  probably  the  one 
that  the  French  had  for  exhibition  purposes,  but  not  the  one 
they  intended  to  use.  Having  tried  all  the  various  forms 
of  screws  and  other  objects  shown  in  Fig.  9,  I  made  some 
sheet  metal  screws ;  also  a  screw  which  consisted  of  a  steel 
frame  covered  with  woven  fabric,  and  which  was  identical 
with  screws  that  I  had  seen  described  in  various  works 


4U  ARTIFICIAL    AND    NATURAL    FLIGHT. 

relating  to  aerial  navigation.  It  was  found  quite  impos- 
sible to  keep  the  fabric  taut  and  smooth,  and  the  results 
were  very  bad  indeed,  it  being  only  40  per  cent,  as 
efficient  as  a  well-made  wooden  screw. 

Having  thus  ascertained  the  best  form  of  a  screw,  I 
built  up  my  first  large  screws,  which  were  17  feet  10 
inches  in  diameter,  after  the  well-known  manner  of  making 
wooden  patterns  for  casting  steamship  propellers.  Fig.  15 


Fig.  16. — A  fabric-covered  screw  with  a  very  low  efficiency. 

shows  the  form  of  the  end  of  the  blade,  the  middle  of  the 
blade,  and  the  hub.  My  first  pair  of  large  screws  had 
a  pitch  of  24  feet,  but  these  were  too  great  a  drag 
on  the  engine.  I  therefore  made  another  pair  with  16  feet 
pitch  which  greatly  increased  the  piston  speed,  and 
permitted  the  engines  to  develop  much  more  power;  the 
screw  thrust  was  also  increased  just  in  an  inverse  ratio 
to  the  pitch  of  the  screws.  Another  pair  of  screws 


PRINCIPALLY    RELATING   TO    SCREWS.  41 

was  tried  with  14  feet  pitch  and  12  feet  in  diameter, 
but  these  did  not  do  so  well.  My  large  screws  were 
made  with  a  great  degree  of  accuracy  ;  they  were  perfectly 
smooth  and  even  on  both  sides,  the  blades  being  thin  and 
held  in  position  by  a  strip  of  rigid  wood  on  the  back  of 
the  blade.  In  order  to  prevent  the  thrust  from  collapsing 
the  blades,  wires  were  extended  backwards  and  attached 
to  a  prolongation  of  the  shaft.  Like  the  small  screws, 
they  were  made  of  the  very  best  kind  of  seasoned 
American  white  pine,  and  when  finished  were  varnished 
on  both  sides  with  hot  glue.  When  this  was  thoroughly 
dry,  they  were  sand-papered  again  and  made  perfectly 
smooth  and  even.  The  blades  were  then  covered  with 
strong  Irish  linen  fabric  of  the  smoothest  and  best  make. 
Glue  was  used  for  attaching  the  fabric,  and  when  dry 
another  coat  of  glue  was  applied,  the  surface  rubbed  down 
again  and  then  painted  with  zinc  white  in  the  ordinary 
way  and  varnished.  These  screws  worked  exceedingly 
well.  I  had  means  of  ascertaining,  with  a  great  degree  of 
accuracy,  the  thrust  of  the  screw,  the  number  of  turns  per 
minute,  the  speed  of  the  machine,  and,  in  fact,  all  the  events 
that  were  taking  place  on  the  machine.  It  was  found 
that  when  the  screw  thrust  in  pounds  was  multiplied  by 
the  pitch  in  feet,  and  by  the  number  of  revolutions  made 
in  a  minute  of  time,  it  exactly  corresponded  to  the  power 
that  the  engines  were  developing,  and  that  the  amount  of 
loss  in  skin  friction  was  so  small  as  to  be  practically 
negligible. 

In  connection  with  this  subject  I  would  say  that  many 
experimenters  claim  to  have  shown  that  the  skin  friction 
on  screws  is  considerable,  in  fact,  so  great  as  to  be  a  very 
important  factor  in  the  equation  of  flight.  I  am,  however, 
of  the  opinion  that  these  experimenters  have  not  had  well- 
made  screws.  If  the  surface  of  the  screw  is  uneven, 
irregular,  or  rough,  a  considerable  amount  of  energy  is  lost, 
as  shown  in  the  French  screw  and  the  fabric  covered 
screw.  It  is  simply  a  question  of  having  a  screw  well- 
made.  In  those  recently  employed' in  France  (see  Fig.  17), 
the  blades  are  of  hammered  sheet  metal,  the  twist  is  not 
uniform  or  true,  and  what  is  worst  of  all,  the  arm  b 
projects  on  the  back  of  the  blade  and  offers  a  good  deal  of 
resistance  to  the  air.  This  form  of  screw,  however,  is  very 
ingenious ;  as  will  be  seen  by  the  drawing,  the  pitch  and 
diameter  can  be  changed  at  will.  It  is,  however,  heavy, 


42  ARTIFICIAL    AND    NATURAL    FLIGHT. 

wasteful  of  power,  and  altogether  too  small  for  the  work 
it  has  to  do.  The  skin  friction  of  screws  in  a  steamship 
has  led  inventors  to  suppose  that  the  same  laws  relate  to 
screws  running  in  air,  but  such  is  by  no  means  the  case. 


Fig.  17. — The  hub  and  one  of  the  blades  of  the  screw  on  the  Farman 
machine.  The  blade  c,  is  a  sheet  of  metal  riveted  to  the  rod  b,  and 
forms  a  projection  on  the  back  of  the  blade  which  greatly  reduces 
its  efficiency.  The  peculiar  form  of  hub  employed  makes  it  possible 
to  change  the  diameter  and  pitch  of  this  screw  at  will. 

In  designing  a  steamship,  we  have  to  make  a  compromise 
in  regard  to  the  size  of  the  screw.  If  the  screw  is  too 
small,  an  increase  in  diameter  is,  of  course,  an  advantage, 
and  it  may  also  be  an  advantage,  not  only  to  increase  the 


—    S 

J 


n 


14 


ARTIFICIAL    AND    NATURAL    PLIGHT. 


diameter,  but  also  to  reduce  the  pitch ;  however,  a  point 
is  soon  reached  where  the  skin  friction  will  more  than 
neutralise  the  advantages  of  engaging  a  larger  volume  of 
water.  This  is  because  the  water  adheres  to  the  surface ; 
in  fact,  the  skin  friction  of  a  ship  and  its  screw  consumes 
fully  80  per  cent,  of  the  total  power  of  the  engines,  but 
with  an  air  propeller  its  surface  is  not  wetted  and  the  air 
does  not  stick  to  its  surface.  If  made  of  polished  wood, 
the  friction  is  so  extremely  small  as  to  be  almost  untneasur- 


OOOOOOOOOOOOOOo 


Fig.  19.  —Shows  the  form  of  the  blade  of  a  screw  propeller  made  of  sheet 
metal.  It  is  riveted  at  the  edges  and  also  to  the  arm  of  a  screw  with  a 
stiffening  piece  at  the  extreme  end.  However,  it  is  not  necessary  to 
rivet  edges  together.  They  may  be  welded  with  a  flame  of  acetylene 
oxygen  gases. 


Fig.  19a. — Shows  the  manner  of  welding  and  the  finished  edge. 

able.  The  diameter  of  a  well-made  screw  running  in  air  is 
therefore  not  limited  in  any  degree  by  skin  friction,  as  is 
the  case  with  a  screw  running  in  water ;  in  fact,  it  is  rather 
a  question  of  its  weight,  and  its  efficiency  ought  to  increase 
in  direct  ratio  with  its  diameter,  because  the  area  of  the 
disc  increases  with  the  square  of  the  diameter.  The  screw 
slip  is  therefore  reduced  by  one-half  by  simply  doubling 
the  diameter  of  the  screw.  It  will  be  understood  that  by 
doubling  the  diameter  of  the  screw,  four  times  as  much  air 


d 


b 


Fig.  20.— A  new  form  of  hub,  of  great  strength  and  lightness,  for  use  on 
flying  machines. 


46  ARTIFICIAL    AND    NATURAL    FLIGHT. 

will  be  engaged.  If  we  push  this  back  at  half  the  speed, 
we  shall  have  the  same  screw  thrust,  because  the  resistance 
of  the  air  is  in  proportion  to  the  square  of  the  velocity 
that  we  impart  to  it,  so  that  one  just  balances  the  other, 
and  the  diminution  of  wasteful  slip  is  just  in  proportion  to 
the  increase  in  diameter.  In  all  cases,  the  screw  should  be 
made  as  large  as  possible. 

In  the  drawing  (Fig.  18)  I  have  shown  screw  blades  of 
a  proper  shape  to  give  the  best  results — that  is,  providing  a 
metallic  screw  is  employed.  Instead  of  having  the  arm  of 
the  screw  on  the  back  of  the  blade  to  offer  resistance  to  the 
air,  the  arm  should  be  tubular,  flattened,  and  covered  on 
both  sides  with  sheet  metal.  This  particular  formation  not 
only  prevents  the  air  from  striking  the  arm,  but,  at  the 
same  time,  prevents  the  pressure  of  the  air  from  deforming 
the  blade,  so,  if  a  metallic  screw  is  to  be  used,  the 
form  of  blade  which  I  have  shown  will  be  found  much 
superior  to  that  employed  at  the  present  time  on  continental 
flying  machines.  We  should  not  lose  sight  of  the  fact  that 
weight  tells  very  seriously  against  the  success  of  a  flying 
machine,  and  that  no  expense  should  be  spared  to  reduce 
the  weight,  providing  that  it  is  possible  to  do  so  without 
reducing  the  factor  of  safety.  Suppose,  for  example,  that 
we  use  an  ordinary  hub  secured  to  a  solid  shaft  by  a 
common  key.  All  the  parts  have  to  be  made  heavy  in 
order  to  be  sufficiently  strong  to  withstand  the  strain.  In 
the  drawing  (Fig.  20)  I  have  shown  a  hub  which  I  think  is 
quite  as  light  and  strong  as  it  is  possible  to  make  it.  The 
action  of  the  motor  is  often  spasmodic  and  puts  very  great 
strain  upon  the  parts,  and  there  is  a  very  strong  tendency 
for  the  shaft  to  turn  round  in  the  hub.  If  a  key  is  used, 
the  hub  has  to  be  large  and  strong,  and  the  key  of  con- 
siderable size,  otherwise  the  parts  would  be  deformed.  In 
my  own  experiments,  I  have  found  .considerable  difficulty 
in  securing  a  shaft  to  wooden  screws  However,  it  will  be 
seen  in  the  drawings  that  a  series  of  grooves  is  cut  in  the 
shaft  and  that  the  hub  has  internal  projections,  so  that  the 
one  fits  the  other.  This  makes  a  very  strong  connection 
and  is  of  extreme  lightness.  Both  the  hub  and  the  shaft 
should  be  of  tempered  steel.  The  spokes  should  be  hard 
drawn  steel  tubes  with  long  fine  threads,  so  as  to  with- 
stand centrifugal  force.  To  prevent  them  from  rotating  in 
the  hub,  the  nuts  d,  d  are  provided,  which  compress  the 
arms  of  the  steel  hub  so  as  to  grip  the  tube  with  any 


PRINCIPALLY    RELATING    TO    SCREWS.  47 

degree  of  force  required.  It  will  be  seen  that  with  this 
system  the  pitch  of  the  screw  may  be  adjusted  to  some 
extent ;  however,  it  is  better  to  have  all  parts  of  the  screw, 
from  hub  to  centre,  of  the  same  pitch.  A  slight  deviation 
from  this  is  admissible  in  the  experimental  stage,  so  long 
as  the  deviation  from  a  true  screw,  caused  by  rotating  the 
arm,  is  not  greater  than  one  half  of  the  slip  while  in  flight. 
Many  experimenters  have  imagined  that  a  screw  is  just 
as  efficient  placed  in  front  of  a  machine  as  at  the  rear,  and 
it  is  quite  probable  that,  in  the  early  days  of  steamships,  a 
similar  state  of  things  existed.  For  several  years  there 
were  steamboats  running  on  the  Hudson  River,  New  York, 
with  screws  at  their  bows  instead  of  at  their  stern.  In- 
ventors of,  and  experimenters  with,  flying  machines  are  not 
at  all  agreed  by  any  means  in  regard  to  the  best  position 
for  the  screw.  It  would  appear  that  many,  having  noticed 
that  a  horse -propelled  carriage  always  has  the  horse 
attached  to  the  front,  and  that  the  carriage  is  drawn  in- 
stead of  pushed,  have  come  to  the  conclusion  that,  in  a 
flying  machine,  the  screw  ought,  in  the  very  nature  of 
things,  to  be  attached  to  the  front  of  the  machine,  so  as  to 
draw  it  through  the  air.  Railway  trains  have  their 
propelling  power  in  front,  and  why  should  it  not  be  the 
same  with  flying  machines  ?  But  this  is  very  bad  reasoning. 
There  is  but  one  place  for  the  screw,  and  that  is  in  the 
immediate  wake,  and  in  the  centre  of  the  greatest  atmos- 
pheric disturbance.  While  a  machine  is  running,  although 
there  is  a  marked  difference  between  water  and  air  as  far 
as  skin  friction  is  concerned,  still  the  conditions  are  the 
same  as  far  as  the  position  of  the  screw  is  concerned. 
With  a  well-designed  steamship,  the  efficiency  of  the  screw 
is  so  great  as  to  be  almost  unbelievable;  in  fact,  if  a 
steamship  had  never  been  made,  and  the  design  of  one 
should  be  placed  before  the  leading  mathematicians  of  to- 
day, with  the  request  that  they  should  compute  the 
efficiency  of  the  screw,  none  of  them  would  come  anywhere 
near  the  mark.  They  would  make  it  altogether  too  small. 
As  before  stated,  when  a  steamship  is  being  driven  through 
the  water,  the  water  adheres  to  its  sides  and  is  moved 
forward  by  the  ship — that  is,  it  has  acceleration  imparted  to 
it  which  exactly  corresponds  to  the  power  consumed  in 
driving  the  ship  through  the  water.  This,  of  course, 
retards  it,  and  we  find  in  a  well-designed  ship,  not  run 
above  its  natural  speed,  that  about  80  per  cent,  of  the 


48  ARTIFICIAL    AND    NATURAL    FLIGHT. 

power  of  the  engine  is  consumed  in  skin  friction,  or  in 
imparting  a  forward  motion  to  the  water.  Suppose  that 
we  should  take  such  a  ship,  remove  the  screw,  and  tow  it 
through  the  water  with  a  very  long  wire  rope  at  a 
speed  of,  say,  20  miles  an  hour ;  we  should  find  that  the 
water  at  the  stern  of  the  ship  was  moving  forward  at  a 
velocity  of  fully  6  miles  an  hour — that  is,  travelling  in  the 
same  direction  as  the  ship.  By  replacing  the  screw,  and 
applying  engine  power  sufficient  to  give  the  ship  the  same 
speed  of  20  miles  an  hour,  identical  results  would  be 
produced.  The  skin  friction  still  impels  the  water  forward, 
so  that  the  screw,  instead  of  running  in  stationary  water, 
is  actually  running  in  water  moving  in  the  same  direction 
as  the  ship  at  a  velocity  of  6  miles  an  hour.  If  the  slip 
of  the  screw  should  only  be  equal  to  this  forward  motion, 
the  apparent  slip  would  be  nothing ;  in  fact,  the  ship 
would  be  moving  just  as  fast  as  it  would  move  if  the 
screw  were  running  in  a  solid  nut  instead  of  in  the 
yielding  water.  Curiously  enough  there  have  been  cases 
of  negative  slip  in  which  the  actual  slip  of  the  screw  in  the 
water  was  less  than  the  forward  movement  of  the  water, 
and  in  such  cases  a  ship  is  said  to  have  negative  slip.  A 
very  noticeable  case  of  this  kind  occurred  in  the  Koyal 
Navy  in  the  sixties.*  I  was  at  the  time  engaged  in  a  large 
shipbuilding  establishment  in  New  York,  and  remember 
distinctly  the  interest  that  the  case  created  amongst  the 
draughtsmen  and  engineers  of  that  establishment.  Of 
course,  this  apparently  impossible  phenomenon  created  a 
great  deal  of  discussion  on  both  sides  of  the  Atlantic.  It 
appears  that  this  ship  had  been  built  under  an  Admiralty 
Specification  which  called  for  a  screw  of  a  certain  diameter 
and  pitch  with  a  specified  number  of  revolutions  per 
minute,  and  for  a  certain  number  of  knots  per  hour,  also 
that  the  boiler  pressure  should  not  go  above  a  certain 
number  of  pounds  per  square  inch.  When  the  ship  was 
finished  and  went  on  her  trial  trip,  it  was  found  impossible 
to  make  the  full  number  of  turns  called  for  in  the  specifi- 
cation with  the  boiler  pressure  allowable ;  nevertheless, 
the  speed  was  greater  than  the  specification  called  for,  and 
as  speed  was  the  desideratum,  and  not  the  number  of 
revolutions,  the  contractors  thought  their  ship  should  be 
accepted.  Then  arose  a  discussion  as  to  the  diameter  and 

*  The  particulars    relating  to  this    event    are    taken   from  accounts 
published  at  the  time  in  American  papers. 


PRINCIPALLY    RELATING   TO    SCREWS.  49 

pitch  of  the  screw.  It  was  claimed  that  a  mistake  must 
have  occurred.  A  careful  measurement  was  made  in  the 
dry  dock,  and  all  was  found  correct.  Once  more  the  ship 
was  tried,  and  again  her  speed  was  in  excess  of  the  specifi- 
cation, notwithstanding  that  it  was  still  impossible  to  get 
the  specified  number  of  revolutions  per  minute.  Mathe- 
maticians then  took  the  matter  in  hand,  and  it  was  found 
that  the  ship  actually  travelled  faster  than  she  would  have 
done  if  the  screw  had  been  running  in  a  solid  nut. 
Instead  of  a  positive  slip,  the  screw  had  in  reality  a 
negative  slip  ;  but  this  was  not  believed  at  the  time,  and 
the  discussion  and  controversy  continued.  The  ship  was 
tried  again  and  again,  and  always  with  the  same  results. 
This  apparently  inexplicable  phenomenon  was  accounted 
for  in  the  following  manner : — The  hull  of  the  ship  was 
said  to  be  rather  imperfect  and  to  cause  a  considerable 
drag  in  the  water,  so  that,  when  the  ship  was  moving  at 
full  speed,  the  water  at  the  stern  had  imparted  to  it  a 
forward  velocity  greater  than  the  actual  slip. 

What  is  true  of  ships  is  true  of  flying  machines.  Good 
results  can  never  be  obtained  by  placing  the  screw  in  front 
instead  of  in  the  rear  of  the  machine.  If  the  screw  is  in 
front,  the  backwash  strikes  the  machine  and  certainly  has 
a  decidedly  retarding  action.  The  framework,  motor,  etc., 
offer  a  good  deal  of  resistance  to  the  passage  of  the  air, 
and  if  the  air  has  already  had  imparted  to  it  a  backward 
motion,  the  resistance  is  greatly  increased.  The  framework 
will  always  require  a  considerable  amount  of  energy  to 
drive  it  through  the  air,  and  the  whole  of  this  energy  is 
spent  in  imparting  a  forward  motion  to  the  air,  so  if  we 
place  the  propelling  screw  at  the  rear  of  the  machine 
in  the  centre  of  the  greatest  atmospheric  resistance, 
it  will  recover  a  portion  of  the  lost  energy,  as  in  the 
steamship  referred  to.  It  will,  therefore,  be  seen  that 
when  the  screw  is  at  the  rear,  it  is  running  in  air  which 
is  already  moving  forward  with  a  considerable  velocity, 
which  reduces  the  slip  of  the  screw  in  a  corresponding 
degree.  I  have  made  experiments  with  a  view  of  proving 
this,  which  I  shall  mention  further  on,  and  which  ought  to 
leave  no  chance  for  future  discussion. 

My  first  experiments  had  shown  that  wooden  aeroplanes 
did  much  better  than  any  of  the  fabric  covered  aeroplanes 
that  I  was  able  to  make  at  that  time,  but  as  wood  was 
quite  out  of  the  question  on  my  large  machine  on  account 


50  ARTIFICIAL    AND    NATURAL    FLIGHT. 

of  its  weight,  it  was  necessary  for  me  to  conduct  experi- 
ments with  a  view  of  ascertaining  the  relative  values  of 
different  fabrics.  For  this  purposes,  I  made  the  little 
apparatus  shown  (Fig.  21).  This  was  connected  to  a  tan 
blower  driven  by  a  steam  engine  having  a  governor  that 
worked  directly  on  the  point  of  cut-off.  The  speed  was, 
therefore,  quite  uniform  and  the  blast  of  air  practically 
constant.  I  had  a  considerable  number  of  little  frames  cut 
out  of  sheet  steel,  and  to  these  I  attached  various  kinds  of 
fabric,  such  as  ordinary  satin,  white  silk,  closely  woven 
silk,  linen,  various  kinds  of  woollen  fabrics,  including  some 


Fig.  21.— Small  apparatus  for  testing  fabrics  for  aeroplanes,  the  material 
being  subjected  to  an  air  blast  in  order  to  test  its  lifting  effect  as 
compared  with  its  tendency  to  travel  with  the  blast. 

very  coarse  tweeds,  also  glass-paper,  tracing  linen,  and  the 
best  quality  of  Spencer's  balloon  fabric.  The  blast  of  air 
was  not  large  enough  to  cover  the  whole  surface  of  the 
aeroplanes,  so  that  the  character  of  the  back  of  the  frames 
was  of  no  account.  The  first  object  experimented  with 
was  a  smooth  piece  of  tin.  When  this  was  placed  at  an 
angle  of  1  in  14,  it  was  found  that  the  drift  or  tendency  to 
travel  in  the  direction  of  the  blast  was  just  one-fourteenth 
part  of  the  upward  tendency,  or  lift.  This  was  exactly 
as  it  should  have  been.  Upon  changing  the  angle  to 
1  in  10,  a  similar  thing  occurred ;  the  lift  was  ten  times 


52  ARTIFICIAL    AND    NATURAL    FLIGHT. 

the  drift.  I,  therefore,  considered  the  results  obtained 
with  the  sheet  of  tin  as  unity,  and  gave  to  every  other 
material  experimented  with/a  coefficient  of  the  unity  thus 
established.  Upon  testing  a  frame  covered  with  tightly- 
drawn  white  silk,  a  considerable  amount  of  air  passed 
through,  and  with  an  angle  of  1  in  14,  the  lift  was  only 
about  double  the  drift.  A  piece  of  very  open  fabric, 
a  species  of  buckram,  was  next  tried,  and  with  this  the 
lift  and  drift  were  about  equal.  With  closely-woven, 
shiny  satin  the  coefficient  was  about  '80;  with  a  piece 
of  ordinary  sheeting  the  coefficient  was  '90 ;  with  closely  - 
woven,  rough  tweeds,  '70 ;  and  with  glass-paper  about  '75. 


Fig.  23. — Apparatus  for  testing  aeroplanes,  condensers,  etc.,  in  an 
blast.     The  opening  is  3  feet 
shown  in  position  for  testing. 


blast.     The  opening  is  3  feet  square.      Thin  brass  sustainers  are 
n  fo 


With  a  piece  of  tracing  linen  very  tightly  drawn,  results 
were  obtained  identical  with  those  of  a  sheet  of  tin,  and 
with  Spencer's  balloon  fabric  the  coefficient  was  about  '99. 
I,  therefore,  decided  to  cover  my  aeroplanes  with  this 
material.  It  will  be  observed  that  the  apparatus  is  so 
arranged  that  both  the  lift  and  the  drift  can  be  easily 
measured. 

In  order  to  ascertain  the  resistance  encountered  by 
various  shaped  bodies  driven  at  various  speeds  through 
the  air,  the  best  form  of  aeroplanes,  and  the  efficiency  of 
atmospheric  condensers,  I  made  the  apparatus  shown  in 
Figs.  22  and  23.  The  smaller  and  straight  portion  of  this 


PRINCIPALLY    RELATING  TO   SCREWS. 


ct 


apparatus  was  12  feet  long  and  exactly  3  feet  square 
inside,  and  was  connected  as  shown  to  a  shorter  box 
4  feet  square.  Two  strongly  made  wooden  screws  6,  6 
and  d,  were  attached  to  the  same  shaft.  These  screws 
had  two  blades  each,  and  while  one  pair  of  blades  was  in 
a  vertical  position,  the  other  was  in  a  horizontal  position. 
I  interposed  between  the  screws,  slats  of  thin  wood 
arranged  in  the  manner  shown  at  d,  d;  this  was  to 
prevent  rotation  of  the  air.  At  e  I  placed  vertical  slats 
of  thin  wood,  and  horizontal  slats  of  the  same  size  at  /. 
At  g  two  wide  and  thin  boards, 
sharp  at  both  edges  and  made  in 
the  form  of  the  letter  X,  were 
placed  in  the  box  as  shown  in 
section  XY.  An  engine  of  100 
H.P.  with  an  automatic  variable 
cut-off  was  employed  which  gave 
to  the  screws  a  uniform  rate  of 
rotation,  and  as  the  engine  had 
no  other  work  to  do,  the  governor 
could  be  arranged  to  give  varying 
speeds  such  as  were  required  for 
the  experiments.  The  objects  to 
be  tested  were  attached  to  the 
movable  bars.  In  the  drawing, 
the  aeroplane  k,  k  is  shown  in 
position  for  testing.  This  appar- 
atus was  provided  with  a  rather 
complicated  set  of  levers,  which 
permitted  not  only  the  measure- 
ment of  the  lift  of  the  objects  Fig.  24  - C ^-sect/io ns  of 
experimented  with,  but  also  that  foTas^ertSning^he  co- 

of    the   drift.      The   principle   em-  efficient  of  different  forms. 

plo37ed  in  this   apparatus  was  a 

modification  of  the  ordinary  weighing  apparatus  used  by 
grocers,  etc.  The  first  object  tested  was  a  bar  of  wood 
exactly  2  inches  square  shown  in  Fig.  24.  This  was  placed 
in  such  a  manner  that  the  wind  struck  squarely  against  the 
side  as  shown  in  the  drawing,  and  with  a  wind  of  49  miles 
per  hour,  it  was  found  that  the  drift  or  tendency  to  move 
with  the  air  was  516  Ibs.;  at  the  same  time,  the  wind 
on  my  instrument  gave  a  pressure  of  2  Ibs.  on  a  normal 
plane  6  inches  square.  The  velocity  of  the  wind  was 
ascertained  by  an  anemometer  of  the  best  London  make. 


54 


ARTIFICIAL    AND    NATURAL    PLIGHT. 


Upon  turning  the  same  bar  of  wood  in  the  position  shown 
at  b,  the  drift  mounted  to  5'47  Ibs.  A  round  bar  of  wood, 
2  inches  in  diameter,  shown  at  c,  gave  a  dritt  ot  2W  Ibs. 
These  experiments  were  repeated  with  a  wind  velocity  ot 
40  miles  per  hour,  when  it  was  found  that  the  drift  ot  a 
was  4-56  Ibs.,  and  that  of  the  round  bar,  2'80  Ibs.  It  will 


xperir 
purpose  of  ascertaining  their  coefficients  as  relates  to  a  normal  plane. 

be  seen  from  these  experiments  that  the  power  required 
for  driving  bars  or  rods  through  the  air  is  considerably 
greater  than  one  would  have  supposed.  The  next  object 
experimented  with  was  a,  Fig.  25.  When  this  was  subject 
to  a  wind  of  40  miles  an  hour,  the  drift  was  0-78  Ib. 
Upon  reversing  this  bar — that  is,  putting  the  thin  edge 


PRINCIPALLY    RELATING   TO    SCREWS. 


55 


instead  of  the  thick  edge  next  to  the  wind— the  drift 
mounted  to  1'22  Ibs.;  6  showed  a  drift  of  0'28  Ib.  with 
the  thick  edge  to  the  wind,  and  0'42  Ib.  with  the  thin 
edge  to  the  wind ;  e  showed  a  drift  of  0'23  Ib  with  the 
thick  edge  to  the  wind,  and  0'59  Ib.  with  the  thin  edge  to 
the  wind;  and  d,  which  was  the  same  thickness  as  the 
others  and  1 2  inches  wide,  both  edges  being  alike,  showed 
a  drift  of  only  0'19  Ib.  These  experiments  show  in  a 
most  conclusive  manner  the  shapes  that  are  most  advan- 
tageous to  use  in  constructing  the  framework  of  flying 
machines.  Aeroplane  e,  Fig.  26,  when  placed  on  the 


Angle  One  in  Twenty. 


Angle  One  in  ^Sixteen,. 

Fig.  26.  — A  flat  aeroplane  placed  at  different  angles. 

machine  in  a  horizontal  position  showed  neither  lift  nor 
drift,  but  upon  placing  it  at  an  angle  of  1  in  20,  as  shown 
at  /,  the  lift  was  3'98  Ibs.  and  the  drift  0'30  Ib.  with 
a  wind  velocity  of  40  miles  per  hour.  At  this  low  angle 
the  blade  trembled  slightly.  Upon  placing  the  same  plane 
at  an  angle  of  1  in  16  as  shown  at  g,  the  lift  was  4%59  Ibs. 
and  the  drift  0'53  Ib.  It  will  be  observed  that  the 
underneath  side  of  this  plane  is  perfectly  flat.  The  next 
experiment  was  with  planes  slightly  curved,  as  shown  in 
Fig.  27.  The  aeroplane  a  was  16  inches  wide,  very  thin, 
and  only  slightly  curved.  When  set  at  a  very  low  angle, 


56  ARTIFICIAL    AND    NATURAL    FLIGHT. 

it  vibrated  so  as  to  make  the  readings  very  uncertain, 
but  when  set  at  an  angle  of  1  in  10  it  lifted  9'94  Ibs. 
with  a  drift  of  1-12  Ibs.  By  slightly  changing  the  angle 
it  was  made  to  lift  10'34  Ibs.  with  a  drift  of  T23  Ibs 
the  wind  velocity  being  41  miles  per  hour.  Aeroplane  b 
12  inches  wide,  Fig.  27,  when  placed  at  an  angle  of  1m  14 
with  an  air  blast  of  41  miles  per  hour,  gave  a  hit  ot 
5-28  Ibs.  with  a  drift  of  0'44  lb.;  at  an  angle  of  1  in  12 
the  lift  was  5'82  Ibs.  and  the  drift  05  lb.;  at  an  angle  ot 
1  in  10  the  lift  was  675  Ibs.  and  the  drift  073  lb.;  with  an 
angle  of  1  in  8  the  lift  was  7  75  Ibs.  and  the  drift  1  lb. ; 


.     16"     -   - 


Fig.  27.  — Group  of  aeroplanes  used  in  experimental  research.  Although 
shown  the  same  size  in  the  drawing,  aeroplane  a  was  16  inches  wide, 
and  b  and  c,  12  inches  wide. 

with  an  angle  of  1  in  7  the  lift  was  8*5  Ibs.  and  the  drift 
1-25  Ibs. ;  at  an  angle  of  1  in  6  the  lift  was  9 '87  Ibs.  and 
the  drift  171  Ibs.  Aeroplane  c,  Fig.  27,  which  had  more 
curvature  than  6,  when  run  in  a  horizontal  position,  gave 
a  considerable  lift,  and  when  raised  to  an  angle  of  1  in  12 
it  gave  a  lift  of  6'12  Ibs.  with  a  drift  of  0'54  lb.  In 
another  experiment  at  the  same  angle,  it  gave  a  lift  of 
6-41  Ibs.  with  a  drift  of  0'56  lb.;  at  an  angle  of  1  in  16  it 
gave  a  lift  of  5*47  Ibs.  with  a  drift  of  0'37  lb. ;  at  an  angle 
of  1  in  10  it  gave  a  lift  of  6'97  Ibs.  and  a  drift  of  070  lb. ; 
at  an  angle  of  1  in  8  it  gave  a  lift  of  8'22  Ibs.  with  a  drift 


PRINCIPALLY    RELATING   TO   SCREWS.  57 

of  1'08  Ibs. ;  at  an  angle  of  1  in  7  it  gave  a  lift  of  9'94  Ibs. 
with  a  drift  of  T45  Ibs. ;  at  an  angle  of  1  in  6  it  gave  a  lift 
of  10-34  Ibs.  and  a  drift  of  175  Ibs.  This  plane  was  then 
carefully  set  so  that  both  the  forward  and  aft  edges  were 
exactly  the  same  height,  and  with  a  wind  blast  of  41  miles 
per  hour  it  gave  a  lift  of  2'09  Ibs.  with  a  drift  of  0-21  Ib. 
It  was  then  pitched  1  in  18  in  the  wrong  direction,  and  at 
this  point,  the  lifting  effect  completely  disappeared,  while 
the  drift  was  practically  nothing. 

When  the  aeroplane  a  (Fig.  28)  was  placed  in  a  hori- 
zontal position,  and  the  apparatus  carefully  balanced,  it 
showed  at  a  wind  velocity  of  40  miles  an  hour,  a  lift  of 
1-56  Ibs.,  and  a  drift  of  0  08  Ib. ;  at  an  angle  of  1  in  20,  a 
lift  of  3'62  Ibs.  and  a  drift  of  0'21  Ib. ;  at  an  angle  of  1  in 
16,  a  lift  of  4-09  Ibs.  with  a  drift  of  0'26  Ib. ;  at  an  angle 


Fig.  28.— An  8 -inch  aeroplane  which  did  very  well.  This  aeroplane 
gave  decided  lifting  effect  when  the  bottom  side  was  placed  dead 
level,  as  shown  at  a. 

of  1  in  14,  a  lift  of  4'5  Ibs.  and  a  drift  of  0'33  Ib.;  at  an 
angle  of  1  in  12,  a  lift  of  5  Ibs.  and  a  drift  of  043  Ib. ; 
at  an  angle  of  1  in  10,  a  lift  of  575  Ibs.  and  a  drift  of 
0  60  Ib.  j  at  an  angle  of  1  in  8,  a  lift  of  675  Ibs.  and  a  drift 
of  0-86  Ib.  The  blast  was  then  increased  to  a  velocity  of 
47-33  miles  an  hour,  when  it  was  found  that  the  lift  at 
an  angle  of  1  in  16  was  5  Ibs.  and  the  drift  0'33  Ib.  It  will 
be  observed  that  this  aeroplane  was  only  8  inches  wide, 
while  the  others  were  12  inches  or  more.  They  were 
all  rather  more  than  3  feet  long,  but  the  width  of  the 
blast  to  which  they  were  subjected  was  exactly  3  feet, 
and  they  were  placed  as  near  to  the  end  of  the  trunk  as 
possible.  .  „ 

The  next   experiments   were   made   with   the  view   ot 
ascertaining  what  effect  would  be  produced  when  objects 


;,S  ARTIFICIAL   AND    NATURAL    FLIGHT. 

were  placed  near  to  each  other  (see  Fig.  29).     Two  bars  of 
wood  2  inches  thick,  and  shaped  as  shown  in  the  drawing, 


Fig.  29.— Resistance  dxie  to  placing  objects  in  close  proximity 
to  each  other. 

were  placed  on  the  machine  and  subjected  to  a  blast  of  41 
miles  per  hour  ;  the  drift  at  various  distances  from  center 
to  center  was  as  follows : — 


24  inches  centers, 

22 

20 

18 

16 

14 

12 

10 

8 

6 

4 


drift  6    ozs. 
„      6      „ 
6      „ 


64 

7 
7f 


PRINCIPALLY    RELATING   TO    SCREWS.  59 

It  will  be  seen  by  this  that  the  various  members  con- 
stituting the  frame  of  a  flying  machine  should  not  be 
placed  in  close  proximity  to  each  other. 

A  bar  of  wood  similar  in  shape  to  d  (Fig.  25),  but  being 
9  inches  wide  instead  of  12  inches,  was  mounted  in  a  wind 
blast  of  41  miles  an  hour,  with  the  front  edge  3'31  inches 
above  the  rear  edge,  and  this  showed  a  lift  of  7  08  Ibs.  and 
a  drift  of  3'23  Ibs.  When  the  angle  was  reduced  to  -'31 
inches,  it  gave  a  lift  of  4'53  Ibs.  with  a  drift  of  0'78  -lb., 
and  with  the  angle  reduced  to  1*31  inches,  the  lift  was 
3-37  Ibs.  and  the  drift  0'5  Ib.  It  will,  therefore,  be  seen 
that  even  objects  rounded  on  both  sides  give  a  very  fair 
lift,  and  in  designing  the  framework  of  machines  advantage 
should  be  taken  of  this  knowledge.  The  bar  of  wood  c 
(Fig.  25)  was  next  experimented  with.  With  the  sharp 
edge  to  the  wind,  and  with  the  front  edge  2  inches  higher 
than  the  rear  edge,  the  lift  was  2*54  Ibs.  and  the  drift  0  76 
Ib.  By  turning  it  about  so  that  the  wind  struck  the  thick 
edge,  the  lift  was  4-45  Ibs.  and  the  drift  0'47  Ib.  This 
seemed  rather  remarkable,  but,  as  it  actually  occurred,  I 
mention  it  for  other  people  to  speculate  upon.  It,  how- 
ever, indicates  that  we  should  take  advantage  of  all  these 
peculiarities  of  the  air  in  constructing  the  framework  of  a 
machine,  which  in  itself  is  extremely  important,  as  I  find 
that  a  very  large  percentage  of  the  energy  derived  from 
the  engines  is  consumed  in  forcing  the  framework  through 
the  air.  It  is  quite  true  that  a  certain  amount  of  this 
energy  may  be  recovered  by  the  screw,  provided  that  the 
screw  runs  in  the  path  occupied  by  the  framework.  Still, 
it  is  much  better  that  the  framework  should  be  so  con- 
structed as  to  offer  the  least  possible  resistance  to  the  air, 
and,  as  far  as  possible,  all  should  be  made  to  give  a  lifting 
effect. 

Having  ascertained  the  lifting  effect  of  wooden  aero- 
planes of  various  forms  and  at  varying  velocities  of  the 
wind,  and,  also,  the  resistance  offered  by  various  bodies 
driven  through  the  air,  I  next  turned  my  attention  to  the 
question  of  condensation.  I  wished  to  recover  as  much 
water  as  possible  from  my  exhaust  steam.  I  had  already 
experimented  with  Mr.  Horatio  Philipps'  sustainers,  and  I 
found  that  their  lifting  enect  was  remarkable.  A  curious 
thing  about  these  aeroplanes  was  that  they  gave  an 
appreciable  lift  when  the  front  edge  was  rather  lower  than 
the  rear.  I  therefore  determined  to  take  advantage  of  this 


flO  ARTIFICIAL   AND  ^NATURAL    FLIGHT. 

peculiar  phenomenon,  and  to  make  my  condenser  tubes  as 
far  as  possible  in  the  shape  of  Mr.  Philipps  sustamers. 
Ficr  30  shows  a  section  of  one  of  these  tubes,  in  which  a,  a 
is  the  top  surface,  b  a  soldered  joint,  and  c  the  steam  space. 


Fig.  30.— Cross-section  of  condenser  tube,  made  in  the  form  of  Philipps' 
sustainers,  in  which  c  is  the  steam  passage. 

These  were  mounted  on  a  frame  as  shown  at  a  (Fig.  31). 
I  had  already  found  that  bodies  placed  near  to  each  other 
offered  an  increased  resistance  to  the  air,  but  by  placing 


Fig.  31. — The  grouping  of  condenser  tubes,  made  in  the  form  of  Philipps' 
sustainers.  This  arrangement  is  very  effective,  condenses  the  steam 
or  cools  the  water,  and  gives  a  lifting  effect  at  the  same  time.  The 
shape  and  arrangement  of  tubes  shown  at  b,  I),  although  effective  as 
a  condenser,  produce  no  lifting  effect,  but  a  rather  heavy  drift. 

these  sustainers  in  the  manner  shown  this  was  avoided,  as 
the  air  had  sufficient  space  to  pass  through  without  being 
either  driven  forward  or  compressed.  It  was  found  by 
experiment  that  the  arrangement  of  tubes  or  sustainers, 


PRINCIPALLY    RELATING   TO    SCREWS.  61 

shown  at  d,  d  (Fig.  31),  was  very  efficient  as  a  condenser, 
but  it  gave  a  very  heavy  drift  and  no  lifting  effect  at 
all ;  whereas,  on  the  other  hand,  the  arrangement  shown 
at  a  was  equally  efficient,  and,  at  the  same  time,  gave  a 
decided  lifting  effect.  When  twelve  of  these  tubes  or 
sustainers  were  placed  at  an  angle  of  1  in  12,  the  lifting 
effect  was  12 -63  Ibs.  and  the  drift  2 -06  Ibs.  It  was  found, 
however,  that  a  good  deal  of  the  drift  was  due  to  the  wind 
getting  at  the  framework  that  was  used  for  holding  .the 
sustainers  in  position.  With  a  wind  velocity  of  40  miles 
an  hour  and  a  temperature  of  62°  F.,  2'25  Ibs.  of  water 
were  condensed  in  five  minutes,  and,  while  running,  the 
back  edge  of  the  sustainers  was  quite  cool.  At  another 
trial  of  the  same  arrangement  under  the  same  conditions, 
the  lift  was  11  Ibs.  and  the  drift  2'63  Ibs.  It  is  quite 
possible  on  this  occasion  that  the  metal  was  so  extremely 
thin  that  the  angles  were  not  always  maintained ;  conse- 
quently, that  no  two  readings  would  be  alike.  It  was 
found  at  this  point  that  the  belt  was  slipping,  and  a  larger 
pulley  was  put  on  the  driving  shaft  of  the  screws;  and 
under  these  conditions,  with  a  wind  of  49  miles  per  hour 
and  an  angle  of  1  in  8,  the  lifting  effect  ran  up  to  14'87  Ibs. 
with  a  drift  of  2*44  Ibs.,  and  the  condenser  delivered  2*87 
Ibs.  of  water  from  dry  steam  in  five  minutes.  The  weight 
of  metal  in  this  condenser  was  extremely  small,  the  thick- 
ness being  only  about  -tb-  of  an  incn-  This  condenser 
delivered  the  weight  of  the  sustainers  in  water  every  five 
minutes.  They  should,  however,  have  been  twice  as  heavy. 
Cylinder  oil  was  now  introduced  with  the  steam  in  order 
to  ascertain  what  effect  this  would  have.  After  seven 
minutes'  steaming,  2'25  Ibs.  of  water  were  condensed  in 
five  minutes.  It  will  be  seen  from  these  experiments  that 
an  atmospheric  condenser,  if  properly  constructed,  is  fairly 
efficient.  Koughly  speaking,  it  requires  2,400  times  as 
much  air  in  volume  as  of  water  to  use  as  a  cooling  agent. 
With  the  steam  engine  condenser  only  a  relatively  small 
amount  of  water  is  admitted,  and  this  is  found  to  be 
sufficient ;  but  in  an  atmospheric  condenser  working  in  the 
atmosphere,  it  must  be  as  open  as  possible,  so  that  no  air 
which  has  struck  one  heated  surface  can  ever  come  in 
contact  with  another. 


CHAPTER   V. 

EXPERIMENTS   WITH   APPARATUS   ATTACHED 
TO    A  ROTATING   ARM. 

FROM  what  information  I  have  at  hand,  it  appears  that 
Prof.  Langley  made  his  first  experiments  with  a  small 
apparatus,  using  aeroplanes  only  a  few  inches  in  dimensions 
which  travelled  round  a  circle  perhaps  12  feet  in  diameter. 
With  this  little  apparatus,  he  was  able  to  show  that  the 
lifting  effect  of  aeroplanes  was  a  great  deal  more  than  had 
previously  been  supposed  After  having  made  these  first 
experiments,  he  seems  to  have  come  to  the  conclusion  that 
Newton's  law  was  erroneous.  Shortly  after  Langley  had 
made  these  experiments  on  what  he  called  a  whirling 
table,  which,  however,  was  not  a  very  appropriate  name,  I 
made  an  apparatus  myself,  but  very  much  larger  than  that 
employed  by  Prof.  Langley.  I  reckoned  the  size  of  my 
aeroplanes  in  feet,  where  he  had  reckoned  his  in  inches. 
The  circumference  of  the  circle  around  which  my  aeroplanes 
were  driven  was  exactly  200  feet,  and  shortly  after  this 
Langley  constructed  another  apparatus,  the  same  dimen- 
sions as  my  own.  From  an  engraving  which  I  have  before 
me,  it  appears  that  he  constructed  an  extremely  large 
wooden  scale  beam  supported  by  numerous  braces,  but  free 
to  be  tilted  in  a  vertical  direction  after  the  manner  of  all 
other  scale  beams.  As  this  apparatus  was  of  great  weight 
and  offered  enormous  resistance  to  the  air,  I  do  not  under- 
stand how  it  was  possible  to  obtain  any  very  correct 
readings,  especially  as  it  was  in  the  open  and  subject  to 
every  varying  current  of  air. 

In  constructing  my  apparatus,  which  is  shown  in  the 
photographs,  and  also  in  a  side  elevation  (Fig.  32),  I  aimed 
at  making  the  apparatus  very  light  and  strong,  avoiding  as 
far  as  possible  atmospheric  resistance.  In  the  drawing,  a, 
is  a  thick  seamless  steel  pipe  6  inches  diameter;  6,  is  a  cast- 
iron  pedestal  firmly  bolted  to  d,  and  connected  to  a  large 
cast-iron  spider  embedded  in  hydraulic  cement;  by  this 
means  great  rigidity  and  stiffness  were  obtained,  n,  n  was 
formed  of  strong  Georgia  pine  planks  2  inches  thick,  and 


11} 


ARTIFICIAL    AND    NATURAL    FLIGHT. 


strongly  bolted  together.  The  two  members  of  the  long 
radial  arm  h,  h,  were  made  of  Honduras  mahogany,  an 
extremely  strong  wood,  and  had  their  edges  tapered  off  as 
shown  at  y,  y.  The  power  was  transmitted  from  a  small 
steam  engine  provided  with  a  sensitive  governor  through 
the  shaft/,/.  In  the  base  c,  of  the  casting  b,  was  placed  a 
pair  of  tempered  steel  bevel  gears,  giving  to  the  vertical 
shaft  a  high  velocity.  From  a  pulley  on  the  top  of  this 
shaft,  the  belt  i,  was  run  through  the  arms  h,  h,  as  shown  in 
section  y,  y.  This  gave  a  rapid  rotation  to  the  screw  shaft 
in  a  very  simple  manner.  The  operation  of  the  machine 


Fig.  33. — A  screw  and  fabric  covered  aeroplane  in  position  for  testing. 

was  as  follows : — the  aeroplane  g,  to  be  tested  was  secured 
to  a  sort  of  weighing  apparatus  which  is  shown  in  detail 
(Fig.  36),  and  the  screw  attached  to  the  shaft.  Upon 
starting  the  engine,  a  very  rapid  rotation  was  given  to  the 
screw  which  caused  the  radial  arm  to  travel  at  a  high 
velocity,  the  whole  weight  resting  on  a  ball  bearing  at  w. 
The  radial  arms  and  all  of  their  attachments  were  balanced 
by  a  cigar-shaped  lead  weight  8,  which  was  secured  to  a 
sliding  bar  so  as  to  make  it  easily  adjustable.  The  thrust 
of  the  screw  caused  the  screw  shaft  to  travel  longitudinally, 
and  this  was  opposed  by  a  spring  connected  by  a  very 


EXPERIMENTS  WITH  APPARATUS.  65 

thin  and  light  wire  to  the  pointer  of  the  index  o.  As  the 
apparatus  rotated  rather  slowly  on  account  of  its  great 
diameter,  it  was  quite  possible  to  observe  the  lift  while  the 
machine  was  running  at  its  highest  speed.  The  aeroplanes 
were  mounted  after  the  manner  of  the  tray  of  a  grocer's 
scales  (see  Fig.  36),  and  the  lift  of  the  aeroplane  was 
determined  by  what  it  would  lift  at  r— that  is,  while 
the  machine  was  running  at  a  given  speed,  iron  or  lead 
weights  were  placed  in  the  pail  r,  until  the  lift  of  'the 
aeroplane  was  exactly  balanced,  and  then,  in  order  to 


Fig.  34. — The  rotating  arm  of  the  machine  with  a  screw  and 
aeroplane  attached. 

ascertain  exactly  what  the  lift  was,  the  aeroplane  was 
placed  under  what  might  be  called  a  small  crane,  and 
a  cord,  running  over  a  pulley,  attached.  The  amount  of 
weight  necessary  to  lift  the  plane  into  the  same  position 
that  it  occupied  while  running  was  taken  as  its  true 
lift.  In  order  to  facilitate  experiments  the  gauge  p, 
was  provided.  This  gauge  consisted  of  a  large  glass  tube 
and  the  index  p,  with  a  quantity  of  red  water  at  q.  The 


66  ARTIFICIAL   AND    NATURAL    FLIGHT. 

centrifugal  force  of  rotation  caused  the  red  water  to  rise 
in  the  tube.  This  was  easily  seen,  so  that  if  experiments 
were  being  tried,  we  will  say  at  50  miles  an  hour,  it 
was  always  possible  to  turn  on  steam  until  the  red 
liquid  mounted  to  50.  This  device  was  very  simple 
and  effective,  and  saved  a  great  deal  of  time.  In  order  to 
prevent  the  twisting  of  the  radial  arm,  a  piece  of  stiff 
oval  steel  tube  12  feet  long  was  secured  between  the  arms 
at  j,  and  on  each  end  of  this  tube  were  attached  the  wires 


Fig.  35. — The  little  steam  engine  used  by  me  in  my  rotating  arm  experi- 
ments ;  the  tachometer  and  dynamometer  are  distinctly  shown. 

u,  u.  This  not  only  effectually  supported  the  end  of 
the  arm,  but  at  the  same  time  prevented  twisting  and 
made  everything  extremely  stiff.  Of  course,  while  the 
machine  was  running  at  a  high  velocity,  centrifugal  force 
had  to  be  dealt  with,  and  in  order  to  prevent  this  from 
causing  friction  in  the  articulated  joints  of  the  weighing 
apparatus  (Fig.  36),  thin  steel  wires  k,  k  were  provided. 
As  this  apparatus  was  in  the  open,  it  was  found  that 
the  slightest  movement  of  the  air  greatly  interfered  with 
its  action.  On  one  occasion  when  a  fabric  covered  aero- 


EXPERIMENTS  WITH  APPARATUS.  67 

plane,  4  feet  long  by  3  feet  wide,  was  placed  in  position, 
the  four  corners  being  held  down  by  the  wires  v,  v,  and 
the  apparatus  driven  at  a  high  velocity,  a  sudden  gust  of 
wind  snapped  two  of  the  wires,  broke  the  aeroplane,  and 
the  flying  fragments  smashed  the  screw,  and  this  notwith- 
standing that  each  of  the  four  wires  was  supposed  to  be 
strong  enough  to  resist  at  least  four  times  any  possible 
lifting  that  the  whole  aeroplane  might  be  subjected  to. 

In  order  to  ascertain  the  force  and  direction  of  the 
wind,  I  made  an  extremely  simple  and  effective  apparatus 
which  is  fully  shown  (see  Fig.  38).  Whilst  conducting 
these  experiments  it  occurred  to  me,  when  a  large  aeroplane 
was  used,  that  after  it  had  been  travelling  for  a  consider- 
able time,  it  would  impart  to  the  air  in  the  path  of  its 
travel,  a  downward  motion,  and  that  the  lifting  effect 
would  be  greatly  reduced  on  this  account.  In  order  to 
test  this,  I  provided  four  light  brass  screws  and  mounted 
them,  as  shown  at  x,  on  a  hardened  polished  steel  point 
much  above  their  centre  of  gravity,  so  that  they  balanced 
themselves.  On  account  of  the  absence  of  friction,  they 
were  easily  rotated,  and  responded  to  the  least  breath  of 
air  that  might  be  moving.  One  morning  when  there  was 
a  dead  calm,  I  placed  four  of  these  screws  equidistant 
around  the  whole  circle.  Some  of  them  rotated  very 
slowly  in  one  direction  and  some  in  another ;  some  alter- 
nated, but  all  their  motions  were  extremely  slow.  However, 
upon  setting  the  machine  going  with  a  large  aeroplane  and 
a  powerful  screw,  I  found  after  a  few  turns  that  the  air 
was  moving  downwards  around  the  whole  circle  at  a 
velocity  of  about  2  miles  an  hour,  but  as  the  screw  was 
a  considerable  distance  below  the  aeroplane,  I  estimated 
that  the  actual  downward  velocity  of  the  air  in  which  the 
aeroplane  was  travelling  was  about  4  miles  an  hour. 
The  result  of  my  experiments  are  clearly  shown  in  an 
unpublished  paper  which  I  wrote  at  the  time,  and  as  it  is 
of  considerable  historical  interest,  I  have  placed  it  in  the 
appendix,  notwithstanding  that  there  may  be  certain 
repetitions. 

In  Fig.  36,  a,  a  is  the  body  of  the  apparatus,  partly  of 
gunmetal  and  partly  of  wood.  It  is  provided  with  a  steel 
shaft  to  which  the  screw  h,  is  attached,  and  also  with  a 
cylindrical  pulley  for  taking  the  belt.  The  thrust  of  the 
screw  pushes  the  shaft  inwards  and  records  the  lift  at  o 
(Fig.  32).  The  corners  of  the  aeroplane  g,  g,  are  attached 


68  ARTIFICIAL    AND    NATURAL    PLIGHT. 

by  wires  to  the  steel  plate  e.  b,  b,  is  a  four-arm  spider  for 
holding  the  ends  of  the  parallel  bars  c,  c,  and  d,  d, 
show  vertical  steel  bars  to  which  all  devices  to  be  tested 
are  attached.  In  testing  aeroplanes,  weights  may  be 
placed  at  e,  sufficient  to  balance  the  lifting  effect,  and  then 
by  adding  the  weight  to  the  upward  pull  of  the  aeroplane, 
the  true  lift  of  the  aeroplane  is  obtained.  It  is  also 
possible  to  attach  an  aeroplane  at  e,  that  is,  the  machine 
was  made  to  test  superposed  aeroplanes  if  required.  In 


Fig.  36.— The  machine  attached  to  the  end  of  the  rotating  shaft — a,  a,  the 
body  of  the  machine  ;  6,  b,  four-legged  spider  secured  to  a,  a  ;  c,  c, 
parallel  bars  ;  d,  d,  vertical  member  to  which  the  aeroplane  g,  </  is 
attached  ;  h,  h,  the  screw  ;  /,/,  wires  for  preventing  distortion  of  the 
aeroplane. 

these  experiments,  I  naturally  assumed  that  the  best 
position  for  a  screw  was  at  the  rear  and  in  the  path  of 
the  greatest  resistance,  but  as  some  experimenters  with 
navigable  balloons  placed  the  screw  in  front  in  order 
to  pull  the  apparatus  along  instead  of  to  push  it,  I  made 
experiments  to  see  what  the  relative  difference  might  be. 
In  order  to  do  this,  I  wound  a  large  amount  of  rope  one- 


EXPERIMENTS  WITH  APPARATUS.  69 

half  inch  in  diameter  around  the  whole  apparatus 
forward  of  the  screw,  converting  it  into  an  irregular  mass 
well  calculated  to  offer  atmospheric  resistance.  Upon 
starting  the  engine,  I  was  rather  surprised  to  see  how 
little  retardation  these  ropes  gave  to  the  apparatus.  It 
appeared  to  me  that  nearly  all  of  the  energy  consumed  in 
driving  the  ropes  through  the  air  was  recovered  by  the 
screw.  I  then  removed  the  right-hand  screw  and  replaced 


Fig.  37.— Marking  off  the  dynamometer.  In  order  to  ascertain  the  actual 
amount  of  power  consumed  in  driving  the  propeller,  a  brake  was  put 
on  in  place  of  the  screw,  a  weight  applied,  and  the  engine  run  at  full 
speed.  In  this  way  all  the  uncertain  and  unknowable  factors  were 
eliminated. 

it  by  a  left-hand  screw  of  the  same  pitch  and  dimensions 
(Fig.  37a).  I  then  found  that  the  blast  of  the  screw  blowing 
against  the  tangle  of  ropes  greatly  retarded  the  travel ;  in 
fact,  with  the  same  number  of  revolutions  per  minute,  the 
velocity  fell  off  60  per  cent.  I  think  that  these  experi- 
ments ought  to  show  that  there  is  but  one  place  for  the 
screw,  and  that  is  at  the  stern,  and  in  the  direct  path 
of  the  greatest  atmospheric  resistance. 


70  ARTIFICIAL   AND    NATURAL    FLIGHT. 

Fig.  38  shows  an  original  apparatus  which  I  designed 
and  made  for  my  own  use ;  with  ordinary  anemometers  it 
is  necessary  to  count  the  number  of  turns  per  minute  in 
order  to  ascertain  the  velocity  of  the  wind.  I  wanted 
something  that  would  indicate  the  velocity  and  the 
direction  of  the  wind  without  any  figures  or  formulae. 
I  therefore  made  the  apparatus  shown  in  the  drawing, 
in  which  a,  a,  is  a  metallic  disc  13*54  inches  in  diameter, 
giving  it  an  area  of  exactly  1  square  foot.  This  is 
attached  to  the  horizontal  bar  b,  and  the  whole  mounted 
on  two  bell  crank  levers  as  shown.  When  the  wind  is 
not  blowing,  the  long  arms  of  these  two  levers  assume 
a  vertical  position,  and  the  spiral  spring  h,  is  in  exact 


Fig.  37a.  — Right-and  left-hand  four-blade  screws  used  in  my  experiments 
for  ascertaining  the  comparative  efficiency  between  screws  placed  in 
front  and  in  the  rear  of  the  machine. 

line  with  the  pivots  on  which  these  levers  are  mounted, 
and  has  no  effect  except  to  hold  the  levers  in  a  vertical 
position.  As  the  spring  has  very  little  tension  in  this 
position,  and  as  it  requires  a  considerable  movement  in 
order  to  give  it  tension,  the  arms  c,  c,  and  the  bar  b,  b,  are 
very  easily  pushed  backwards,  but  as  the  distance  through 
which  they  travel  increases,  the  angle  of  the  lever  changes 
and  the  tension  of  the  spring  increases  at  the  same  time, 
so  that  when  the  disc  is  pushed  backwards  to  any  consider- 
able distance,  a  strong  resistance  is  encountered.  Had 
I  made  this  apparatus  so  that  the  pressure  acted  directly 
on  the  spiral  spring,  the  spaces  on  the  index  indicating- 
low  velocities  would  have  been  very  near  together,  while 


EXPERIMENTS  WITH  APPARATUS. 


71 


t  ' 


72  ARTIFICIAL   AND    NATURAL    FLIGHT. 

those  indicating  high  velocities  would  have  been  widely 
separated,  but  with  this  device  properly  designed,  the 
spacing  on  the  index  became  regular  and  even.  The  index 
being  very  large  enabled  one  to  read  it  at  a  considerable 
distance,  and  at  the  same  time,  it  acted  as  a  tail  and  kept 
the  apparatus  face  to  the  wind.  The  spaces  of  the  dial 
were  not  laid  off'  with  a  pair  of  dividers,  but  each  par- 
ticular division  was  marked  by  an  actual  pull  on  the  bar  6, 
through  the  agency  of  a  cord  and  easily  running  pulley 
and  weight.  The  markings,  however,  were  not  correct, 
because  Haswell's  formula  was  employed  in  which  the 
pressure  of  the  wind  against  the  normal  plane  is  consider- 
ably greater  than  with  the  more  recent  formula,  which 
is  now  known  to  be  correct.  Haswell's  formula  was 
V2  x  -005  =  P,  and  the  recent  formula  P  =  O'OOSV2,  where 
P  =  pressure  in  Ibs.  per  square  foot  and  V  =  velocity  in 
miles  per  hour.  In  my  experiments,  I  also  employed  a  very 
well  made  and  delicate  anemometer  by  Negretti  &  Zambra. 


CRYSTAL    PALACE    EXPERIMENTS. 

Having  fully  satisfied  myself  that  aeroplanes  flying 
around  a  circle  200  feet  in  circumference  had  their  lifting 
effect  reduced  to  no  insignificant  degree  by  constantly 
engaging  air  which  had  already  had  imparted  to  it  a  down- 
ward movement  by  a  previous  revolution,  I  determined  to 
make  some  experiments  where  this  trouble  could  not  occur, 
but  the  opportunity  did  not  present  itself  until  after  the 
large  roundabout,  erroneously  described  as  "a  captive 
flying  machine,"  was  put  up  at  the  Crystal  Palace.  This 
presented  a  fine  opportunity  for  making  experiments  at  an 
extremely  high  velocity  around  a  very  large  circle.  I  will 
only  refer  to  a  few  of  these  experiments.  To  a  prolonga- 
tion of  one  of  the  long  arms,  I  attached  a  thin  steel  wire 
rope  about  60  feet  above  the  platform  ;  I  then  attached  to 
this  wire  rope  the  little  device  shown  (Fig.  39),  in  which  a, 
is  an  aeroplane,  5  feet  long  and  1  foot  wide,  placed  at  an 
inclination  of  1  in  20.  Great  care  was  used  in  preparing 
this  aeroplane  to  see  that  it  was  free  from  blemish,  smooth, 
and  without  any  irregularities.  Both  edges  were  sharp 
and  the  curvature  was  about  one-eighth  of  an  inch  on 
the  underneath  side.  It  was  made  relatively  thick  in  the 
middle  where  it  was  attached  to  the  bar  c,  and  thinner  at 


CRYSTAL  PALACE  EXPERIMENTS. 


73 


the  ends.  6,  shows  a  lump  of  lead  just  heavy  enough  to 
balance  the  bar  c,  and  the  tail ;  d,  was  a  light  but  strong 
wooden  frame,  all  the  edges  being  thin  and  sharp  and 
covered  with  a  special  silk  that  Mr.  Cody  had  found 
to  be  best  for  such  purposes.  The  wire  rope  e,  was  attached 
to  the  long  arm  which  I  referred  to.  The  great  length 
of  the  bar  c,  and  the  accuracy  with  which  the  whole  was 
made  and  balanced  caused  the  aeroplane  to  travel  straight 
through  the  air  adjusting  itself  to  all  the  shifting  currents. 
Upon  starting  the  machine  on  a  very  calm  day,  this 


Fig.  39. — Apparatus  for  testing  the  lifting  effect  of  aeroplanes  at  a  low 
angle  and  extremely  high  velocity,  a,  a,  the  aeroplane ;  b,  lead 
weight ;  c,  long  and  slender  pine  rod ;  d,  tail  for  keeping  the 
apparatus  head  on  and  ensuring  its  travelling  straight  through  the 
air  ;  e,  the  point  of  suspension,  also  the  centre  of  gravity.  When  this 
apparatus  was  travelling  at  the  rate  of  80  miles  an  hour,  it  gave 
a  lifting  effect  of  about  36  Ibs. ,  which  is  about  7  Ibs.  per  square  foot. 

apparatus  mounted  as  high  as  the  point  of  support,  some- 
times going  10  or  more  feet  higher  and  sometimes  8  or 
10  feet  lower.  However,  as  a  rule,  it  carried  its  own 
weight  at  a  velocity  of  80  miles  an  hour  around  a  circle 
1,000  feet  in  circumference.  Under  these  conditions,  of 
course,  there  could  be  no  downward  motion  of  the  air 
as  all  the  air  effected  would  be  removed  long  before  it 
could  be  struck  the  second  time  by  the  aeroplane.  I  had 
no  means  of  ascertaining  exactly  how  much  this  plane  did 


74  ARTIFICIAL    AND    NATURAL    FLIGHT. 

actually  lift,  because  the  air  was  always  moving  to  some 
extent,  and  it  was  not  an  easy  matter  to  ascertain  whether 
it  was  above  or  below  the  point  of  support.  I  am  sure, 
however,  that  it  was  as  much  as  36  Ibs.,  or  rather  more 
than  7  Ibs.  to  the  square  foot,  and  this  is  just  what  it 
should  have  lifted,  providing  that  we  consider  the  results 
obtained  by  smaller  planes  placed  in  an  air  blast  of 
40  miles  an  hour  and  at  the  same  angle.  When  these 
experiments  were  finished,  I  made  a  very  small  apparatus 
having  only  about  25  square  feet  of  lifting  surface,  and 
this  carried  the  weight  of  a  man,  in  fact  several  gentlemen 
came  up  from  London  and  went  round  on  it  themselves. 
I  saw,  however,  that.it  was  a  dangerous  practice,  because 
if  the  wind  was  blowing  at  all,  the  apparatus  would  mount 
very  much  above  the  point  of  support  while  travelling 
against  the  wind,  only  to  drop  much  below  the  point 
of  support  on  the  other  side  of  the  circle  where  it  was 
travelling  with  the  wind;  in  fact,  on  one  occasion  the 
apparatus  shown  (Fig.  39)  mounted  in  a  high  wind  fully 
20  feet  above  the  point  of  support  and  came  down  with 
such  a  crash  on  the  other  side  that  it  T}roke  the  wire  rope. 
In  connection  with  this,  it  is  interesting  to  note  that  when 
I  erected  the  first  so-called  "  captive  flying  machine  "  on 
my  own  grounds  at  Thurlow  Park,  I  intended  that  instead 
of  ordinary  boats  such  as  were  ultimately  employed,  each 
particular  boat  should  be  fitted  with  an  aeroplane,  that  the 
engine  should  be  of  200  H.P.,  and  that  the  passengers 
should  actually  be  running  on  the  air,  each  boat  being 
provided  with  a  powerful  electric  motor  in  addition  to  the 
motive  power  that  drove  the  shaft.  Had  this  been  carried 
out  as  was  originally  designed,  it  would  have  removed  the 
apparatus  altogether  from  the  category  of  vulgar  merry-go- 
rounds,  but  such  was  not  to  be.  Unforeseen  circumstances 
were  against  me.  I  had  some  of  these  boats  fitted  up  with 
aeroplanes  and  running  on  my  grounds,  and  two  of  the 
engineers  of  the  London  County  Council  came  out  to  see 
the  apparatus  before  it  was  put  up  for  public  use.  On 
that  occasion  the  wind  was  blowing  a  perfect  gale  |of 
40  miles  an  hour,  and  as  the  boats  travelled  at  the  rate 
of  35  miles  an  hour,  they,  of  course,  encountered  a  wind 
of  75  miles  an  hour  when  passing  against  the  wind,  and 
a  minus  velocity  of  5  miles  an  hour  when  travelling  with 
the  wind  on  the  other  side  of  the  circle.  The  aeroplanes, 
although  of  considerable  size,  were  small  in  relation  to 


CRYSTAL  PALACE  EXPERIMENTS.  75 

weight.     I  had  neglected  to  put  any  weight  in  the  boats, 
and  when  three  of  us  were  studying  the  eccentric  path' 
through  which   the  boats  were  travelling,  suddenly  one 
of  them  in  passing  to  the  windward,  raised  very  much 
above  the  point  of  support  and  plunged  down  with  great 
force  on  the  other  side;   in  fact,  the  shock  was  so  great 
that  it  made  everything  rattle,  but  nothing  was  broken. 
Nevertheless,  the  engineers  said  at  once,  it  would  not  do  to 
run  the  boats  with  those  aeroplanes  ;  it  was  too  dangerous. 
This  would  not,  however,  have  occurred  if  the  boats  had 
been  loaded,  or  the  velocity  of  the  wind  had  been  less.     It, 
however,  demonstrated  what  a   tremendous   lift  may  be 
obtained  from  a  well-made  aeroplane  passing  at  a  high 
velocity    through    the   wind    at    a    sharp    angle.      These 
aeroplanes  were  only  about  12  feet  long  and  5  feet  wide, 
having,  therefore,  60  square  feet  of  surface.     They  were, 
however,  strong,  well-made,  and   perfectly   smooth,  both 
top  and  bottom.     I  would  say  right  here  that  I  am  not 
a  success  as  a  showman — previous  long  years  of  rubbing 
up  against  honest  men  have  disqualified  me  altogether  for 
such  a  profession.     I  was  extremely  anxious  to  go  on  with 
my  experiments.      I  appreciated  fully  that  I  had  made 
a  machine  that  lifted  2,000  Ibs.  more  than  its  own  weight, 
and  I  knew  for  a  dead  certainty  if  I  took  the  matter  up 
again,  got  rid  of  my  boiler  and  water  tank,  and  used  an 
internal   combustion  engine,  such   as   I   thought   I  could 
produce,   that   mechanical    flight   would    soon    be   a  fait 
accompli.      I  had  already  spent  more  than  £20,000,  and 
was  looking  about  for  some  means  of  making  the  thing 
self-supporting.      I   believed   that   the   so-called  "  captive 
flying  machine"  would  be  very  popular,  and   bring  in  a 
lot  of  money,  and  it  would  have  done  so,  if  it  had  been 
put   up   as   originally  designed.      I  proposed   to   use   my 
share  of  the  profits  for  experimental  work  on  real  flying 
machines.      That  I  was  not  far  wrong  in  believing  that 
such  a  machine  would  be  a  success,  is  witnessed  by  the 
fact  that  just  about  the  same  time,  an  American  inventor 
thought  of  the  same  thing,  put  up  some  three  or  four 
machines  the  first  year,  and  the  next  year  about  50.     They 
were  highly  profitable,  and  there  are  fully  140  of  them 
running  at  the  present  time  in  the  U.S.A.     It  is  a  fact 
that  nothing  in  the  way  of  side-shows  at  exhibitions  pi- 
public  resorts  has  ever  had  the  success  of  this  machine  in 
the  U.S.A.,  and  even  the  little  machine  at  Earl's  Court 


76  ARTIFICIAL   AND   NATURAL    FLIGHT. 

took  £325  10s.  in  one  day  and  £7,500  in -a  season.  How- 
ever, this  little  attempt  to  make  one  hand  wash  the  other 
cost  me  no  less  than  £10,400,  not  to  mention  more  than 
a  year  of  very  hard  work.  This  sum  would  have  been 
amply  sufficient  to  have  enabled  me  to  continue  my  ex- 
periments until  success  was  assured. 


77 


CHAPTER  VI. 

HINTS    AS    TO    THE     BUILDING    OP     FLYING 
MACHINES. 

FOR  those  who  really  wish  to  build  a  flying  machine  that 
will  actually  fly  with  very  little  experimental  work,  I  have 
given  an  outline  sketch  sufficiently  explicit  to  enable  a 
skilful  draughtsman  to  make  a  working  drawing  in  which 
Fig.  40  is  a  front  elevation,  Fig.  41  a  side  elevation,  and 
Fig.  42  a  plan.  Fig.  41,  a,  a,  shows  the  two  forward  or 


Fig.  40. — Front  elevation  of  proposed  aeroplane  machine — a,  a,  the  aero- 
planes ;  g,  g,  condenser  ;  /,  the  engine  ;  q,  guard  for  screw  ; 
k,  k,  support  for  wheels. 

main  aeroplanes ;  6,  6,  the  two  after  aeroplanes,  which  are 
smaller  and  shorter ;  c,  the  rudder ;  d,  the  forward  hori- 
zontal rudder ;  e,  the  screw  ;  /,  the  motor ;  g,  the  condenser 
or  cooler ;  h,  the  steering  gear ;  i,  and  j,  atmospheric 
buffers ;  k  and  I,  wheels  attached  to  a  lever  pivoted  to  the 
body  of  the  machine ;  q,  a  shield  for  protecting  the  screw. 
It  will  be  observed  that  the  framework  is  extremely  long, 
and,  consequently,  the  distance  between  the  aeroplanes  is 
very  great ;  but  it  should  be  borne  in  mind  that  the  longer 
the  machine,  the  less  any  change  of  center  of  lifting  effect, 
as  relates  to  the  center  of  gravity,  will  be  felt.  Moreover, 


78 


ARTIFICIAL  AND   NATURAL    FLIGHT. 


HINTS    AS    TO    THE    BUILDING   OF   PLYING    MACHINES. 


7!) 


it  is  much  easier  to  manoeuvre  a  machine  of  great  length 
than  one  which  is  very  short,  because  it  gives  one  more 
time  to  think  and  act.  If  the  length  was  infinitely  great 
the  tendency  to  pitch  would  be  infinitely  small  I  have 
shown  a  steering  gear  consisting  of  a  lever  with  a  handle 
n,  arranged  in  such  a  manner  that  it  moves  both  the 
vertical  rudder  c,  and  the  horizontal  rudder  d,  so  that  the 
man  who  steers  the  machine  has  nothing  to  think  of  except 


j_ 


Fig.  42. — Plan  of  proposed  aeroplane  machine,  in  which  a,  a  are  the 
proposed  superposed  main  aeroplanes ;  b,  b,  the  after  superposed 
aeroplanes ;  c,  c,  the  forward  horizontal  rudder ;  d,  platform  ;  e,  screw ; 
h,  k,  and  i,  i,  pulleys  used  in  communicating  motion  from  the  steering 
gear,  /,  to  the  rudder,  j ;  g,  lever  attached  to  the  aeroplane  or 
rudder,  c,  c,  and  connected  to  the  steering  gear,  /. 

to  point  the  lever  n,  p,  in  the  direction  that  he  wishes  the 
machine  to  go.  This  lever  is  mounted  on  a  universal  joint 
at  h,  and  is  connected  with  suitable  wires  to  the  two 
rudders.  In  order  to  prevent  shock  when  the  machine 
alights,  it  is  necessary  to  provide  something  that  is  strong 
and,  at  the  same  time,  yielding,  and  able  to  travel  through 
a  considerable  distance  before  the  machine  comes  to  a  state 


80  ARTIFICIAL    AND    NATURAL    FLIGHT. 

of  rest.  In  the  machines  which  I  have  seen  on  the  Con- 
tinent, a  very  elaborate  apparatus  is  employed,  which  is 
not  only  very  heavy,  but  also  offers  a  considerable  resist- 
ance to  the  forward  motion  of  the  machine  through  the  air. 
It  consists  of  many  tubes,  very  long  levers  and  heavy  spiral 
springs,  etc.  In  the  device  which  I  am  recommending, 
all  this  is  dispensed  with,  and  something  very  much 
simpler,  cheaper,  and  lighter  is  substituted.  Moreover, 
with  my  proposed  apparatus  a  certain  amount  of  lifting 
effect  is  produced.  The  levers  k,  k,  to  which  the  wheels  are 
attached,  should  be  of  thin  wood,  light  and  strong,  and 
say  about  a  foot  wide,  strongly  pivoted  to  the  frame  and 
held  in  position  by  an  atmospheric  buffer  made  of  strong 
and  thin  steel  tubing,  shown  in  section  (Fig  51).  These 
pneumatic  cylinders  may  be  pumped  up  to  any  degree,  so 
as  to  support  the  weight  of  the  machine,  and  then,  as  it 
comes  down,  the  compression  and  escape  of  air  arrest  its 
motion.  The  condenser  g,  is  placed  in  such  a  position  that 
it  will  act  even  while  the  machine  is  on  the  ground  and  the 
propellers  working.  In  Continental  machines,  very  small 
screw  propellers  are  used.  These  screws  have  probably 
been  made  small  because  the  experimenters  have  found 
that  they  encounter  a  good  deal  of  friction  in  the  atmo- 
sphere, but  this  is  caused  by  imperfect  shape  and  the  rib  of 
steel  at  the  back  of  the  blades.  In  order  to  use  a  small 
screw,  experimenters  have  been  forced  to  use  a  very  quick  - 
running  engine  which  makes  it  necessary  to  have  the 
cylinders  very  short,  so,  in  order  to  get  the  necessary 
power,  they  are  obliged  to  use  no  less  than  eight  cylinders. 
However,  by  increasing  the  diameter  of  the  screw  and 
making  it  of  such  a  form  that  very  little  or  no  atmospheric 
skin  friction  is  encountered,  a  much  better  and  cheaper 
engine  of  a  totally  different  type  may  be  employed.  There 
is  no  reason  why  more  than  four  cylinders  should  be  used, 
but  the  stroke  of  the  piston  and  diameter  of  the  cylinder 
should  be  increased.  Doubtless  Continental  experimenters 
have  an  idea  that,  as  the  engine  cannot  be  provided  with  a 
flywheel,  it  must  have  a  very  large  number  of  cylinders  in 
order  to  give  a  steady  pull  completely  around  the  circle,  and 
thus  avoid  so-called  "dead  centers";  but,  when  we  consider 
the  enormously  high  velocity  of  the  periphery  of  the  screw, 
and  also  take  into  consideration  that  the  momentum  is  in 
proportion  to  the  square  of  the  velocity,  it  is  quite  obvious 
that  there  can  be  no  slowing  up  between  strokes  even  if 


HINTS    AS    TO    THE    BUILDING    OF    FLYING    MACHINES.  81 

only  one  cylinder  should  be  employed  working  on  the 
four-cycle  principle,  in  which  work  is  only  done  one  stroke 
in  four.  Then,  again,  I  find  that  the  weight  of  these 
Continental  engines  can  be  greatly  reduced,  providing  that 
they  are  made  with  the  same  degree  of  refinement  that 
I  employed  in  building  my  steam  engines. 

Recently  there  has  been  a  great  deal  of  discussion  in 
Engineering  and  other  journals  regarding  the  compara- 
tive merits  of  the  aeroplane  system  and  the  helicoptere. 
Some  condemn  both  systems  and  pin  their  faith  to  flapping 
wings.  It  has  been  contended  that  the  screw  propeller 
is  extremely  wasteful  in  energy,  and  that  in  all  Nature 
neither  fish  nor  bird  propels  itself  by  means  of  a  screw. 
As  we  do  not  find  a  screw  in  Nature,  why  then  should  we 
employ  it  in  a  machine  for  performing  artificial  flight  ? 

Why  not  stick  to  Nature  ? .  In  reply  to  this,  I  would 
say  that  even  Nature  has  her  limits,  beyond  which  she 
cannot  go.  When  a  boy  was  told  that  everything  was 
possible  with  God,  he  asked;  "  Could  God  make  a  two-year 
old  calf  in  five  minutes  ?"  He  was  told  that  God  certainly 
could.  "  But,"  said  the  boy,  "  would  the  calf  be  two  years 
old  ?"  It  appears  to  me  that  there  is  nothing  in  Nature 
which  is  more  efficient,  or  gets  a  better  grip  on  the  water 
than  a  well-made  screw  propeller,  and  no  doubt  there 
would  have  been  fish  with  screw  propellers,  providing  that 
Dame  Nature  could  have  made  an  animal  in  two  pieces.  It 
is  very  evident  that  no  living  creature  could  be  made  in  two 
pieces,  and  two  pieces  are  necessary  if  one  part  is 
stationary  and  the  other  revolves ;  however,  the  tails  and 
fins  very  often  approximate  to  the  action  of  the  propeller 
blades ;  they  turn  first  to  the  right  and  then  to  the  left, 
producing  a  sculling  effect  which  is  practically  the  same. 
This  argument  might  also  be  used  against  locomotives.  In 
all  Nature,  we  do  not  find  an  animal  travelling  on  wheels, 
but  it  is  'quite  possible  that  a  locomotive  might  be  made 
that  would  walk  on  legs  at  the  rate  of  two  or  three  miles 
an  hour.  But  locomotives  with  wheels  are  able  to  travel 
at  least  three  times  as  fast  as  the  fleetest  animal  with  legs, 
and  to  continue  doing  so  for  many  hours  at  a  time,  even 
when  attached  to  a  very  heavy  load.  In  order  to  build  a 
flying  machine  with  flapping  wings,  to  exactly  imitate 
birds,  a  very  complicated  system  of  levers,  cams,  cranks, 
etc.,  would  have  to  be  employed,  and  these  of  themselves 
would  wejgh  more  than  the  wings  would  be  able  to  lift. 


82  ARTIFICIAL   AND    NATURAL    FLIGHT. 

However,  it  is  quite  possible  to  approach  very  closely  to 
the  motion  of  a  bird's  wings  with  no  reciprocating  or 
vibrating  parts,  and  without  napping  at  all. 

In  Fig.  43,  I  have  shown  a  plan  of  a  helicoptere  machine 
c 


Fig.  43.—  Plan  of  a  helicoptere  machine  showing  position  of  the  screws. 
Uwing  to  the  tilting  of  the  shaft  forward,  the  blades  present  no  angle 
when  at  d,d,  but  10°  at  c,  c,  while  at/,/ their  angle  above  the  hori- 
zontal is  5  .  The  horizontal  arrows  show  the  direction  of  the  wind 
against  the  machine. 

in  which  two  screws  are  employed  rotating  in  opposite 
directions,  a,  a,  being  the  port  screw ;  b,  6,  the  starboard 
screw;  and  d,  d,  the  platform  for  the  machinery  and 
operator.  The  screws  should  be  20  feet  in  diameter  and 
made  of  wood.  Suppose  now  that  the  pitch  of  these 
screws  is  such  that  the  extremities  of  the  blades  have 


HINTS    AS    TO    THE    BUILDING    OF    FLYING    MACHINES.  83 

an  angle  of  5° ;  if  now  we  tilt  the  shaft  forward  in  the 
direction  of  flight  to  the  extent  of  5°,  we  shall  completely 
wipe  out  the  angle  of  inclination  of  the  blades  when  at  6 
(Fig.  44),  whereas  it  will  be  observed  that  the  pitch  as 
regards  the  horizontal  will  be  increased  to  10°  at  a,  on  the 
outer  side,  and  remain  unchanged  at  c,  and  d.  If  the 
peripheral  velocity  of  the  blades  is,  say,  four  times  the 
velocity  at  which  the  machine  is  expected  to  travel 
the  blades  will  get  a  good  grip  on  the  air  at  c,  d,  but  when 
they  travel  forward  and  encounter  air  which  is  travelling 
at  a  high  velocity  in  the  opposite  direction,  they  assume 
the  position  shown  at  b.  If  the  pitch  of  the  screw  blades 


Fig.  44. — Shows  the  position  of  the  blades  of  a  helicoptere  as  they  pass 
around  a  circle,  when  the  angle  of  the  shaft  and  the  angle  of  the 
blades  are  the  same. 

was  a  little  more  than  the  angle  of  the  shaft,  the  blades  at 
b  would  also  produce  a  lifting  effect,  and  as  the  velocity 
with  which  they  pass  through  the  air  is  extremely  high,  a 
very  strong  lifting  effect  would  be  produced  even  if  the 
angle  was  not  more  than  1  in  40.  By  tracing  the  path  and 
noting  the  position  of  the  ends  of  the  blades  as  they  pass 
completely  around  the  circle  as  shown  (Fig.  44),  it  will  be 
observed  that  they  very  closely  resemble  the  motion  of  a 
bird's  wing.  I  have  no  doubt  that  a  properly  made 
machine  on  this  plan  would  be  highly  satisfactory,  but  one 
should  not  lose  sight  of  the  fact  that  even  with  a  machine 
of  this  type,  well  designed  and  sufficiently  light  to  sustain 
itself  in  the  air  while  flying,  it  would  still  be  necessary  for 


84  ARTIFICIAL   AND   NATURAL    PLIGHT. 

it  to  move  along  rapidly  when  starting  in  order  to  get  the 
necessary  grip  on  the  air.  Upon  starting  the  engine,  in  a 
machine  of  this  kind,  a  very  strong  downward  draught  of 
air  would  be  produced,  and  the  whole  power  of  the  engines 
would  be  used  in  maintaining  this  downward  blast,  but  if 
the  machine  should  at  the  same  time  be  given  a  rapid 
forward  motion  sufficiently  great  to  bring  the  blades  into 
contact  with  new  air,  the  inertia  of  which  had  not  been 
disturbed,  and  which  was  not  moving  downwards,  the 
lifting  effect  would  be  increased  sufficiently  to  lift  the 
machine  off  the  ground.  It  would,  therefore,  work  very 
much  like  an  aeroplane  machine.  It  would  also  be  possible 
to  provide  a  third  screw  of  less  dimensions  and  running  at 
a  less  velocity,  to  push  the  machine  forward,  so  as  not  to 
render  it  necessary  to  give  such  a  decided  tilt  to  the  shafts. 

As  before  stated,  great  care  should  be  taken  in  designing 
and  making  the  framework  of  flying  machines,  and  no 
stone  should  be  left  unturned  in  order  to  arrive  at  the 
greatest  degree  of  lightness  without  diminishing  the 
strength  too  much ;  then,  again,  elasticity  should  be  con- 
sidered. If  we  use  a  thin  tube  all  the  material  is  at  the 
surface,  far  from  the  neutral  centre,  and  great  stiffness  is 
obtained,  but  such  a  tube  will  not  stand  so  much  deflection 
as  a  piece  of  wood  ;  then,  again,  wood  is  cheaper  than  steel, 
and  in  case  of  an  accident,  repairs  are  very  quickly  and 
easily  made.  Wood,  however,  cannot  be  obtained  in  long 
lengths  absolutely  free  from  blemishes.  It  therefore 
becomes  necessary  to  find  some  way  of  making  these  long 
members  of  flying  machines  of  such  wood  as  may  be  found 
suitable  in  the  following  table. 

The  relative  value  of  different  kinds  of  wood  is  shown  in 
this  table,  and  it  will  be  observed  that  some  are  much  more 
suitable  for  the  purpose  than  others.  The  true  value  of  a 
wood  to  be  used  in  flying  machines  is  only  ascertained 
by  considering  its  strength  in  comparison  with  its  own 
weight — that  is,  the  wood  which  is  strongest  in  proportion 
to  its  weight  is  the  best.  It  will  be  seen  that  Honduras 
mahogany  stands  at  the  head  of  the  list,  but  American 
white  pine  is  very  good  for  certain  purposes,  as  it  is  light, 
strong,  easily  obtained,  and  takes  the  glue  very  well 
indeed.  In  Fig.  45,  I  have  shown  a  good  system  of 
producing  the  long  members  necessary  in  flying  machines. 
I  will  admit  that  it  costs  something  to  fit  up  and  produce 
the  kind  of  joints  which  I  have  shown,  but  when  the 


HINTS   AS   TO   THE    BUILDING    OP    PLYING   MACHINES. 


Strength 
per  Sq.  In. 
in  Lbs. 

Weight  of  a 
Cube  Foot 
in  Lbs. 

Relative 
Value. 

Alder,  

50 

Apple,  

49-562 

Ash,  English 

16,000 

52-812 

302-9 

Ash,  White, 

14,000 

43-125 

324-6 

Bamboo,       .... 

6,300 

25 

252 

Beech,  English,    . 

11,500 

53-25 

215-9 

Birch,  

15,000 

45 

333-3 

Box,  African, 

23,000 

... 

,,     France, 

83 

Cedar,  American, 

11,600 

35-062 

330-8 

Deal,  Christiania, 

12,400 

... 

Ebony,          .... 

27,000 

83-187 

324-6 

Elm,     

6,000 

35-625 

168-4 

,,      Eock,  . 

13,000 

50 

260 

Fir,  Norway  Spruce,  . 

32 

... 

,,     Dantzic, 

36-375 

Hackmatack, 

12,000 

37 

324-3 

Hickory,      .... 

11,000 

49-5 

222-2 

Ironwood,    .... 

61-875 

36-375 

Lance,  .         .         .         . 

23,000 

45 

riri 

Lignum-Vitae, 

11,800 

83-312 

141-6 

Lime,   ..... 

50-25 

20,500 

45-5 

450-5 

Mahogany,  Honduras, 
,,           Spanish,     . 

21,000 
12,000 

35 
53-25 

600 
225-3 

Maple,          .... 

46-875 

Oak,  African, 

9,500 

51-437 

184-7 

Canadian, 

54-5 

Dantzic, 

4,200 

47-437 

88-5 

English, 
Live,     .... 

7,571 
16,380 

53-625 
66-75 

141-2 
245-4 

Pa,  seasoned, 

20,333 

White, 

16,500 

53:75 

306-9 

Va, 

25,222 

Pine,  Norway, 

14,000 

46:25 

302-7 

Pitch,  .... 

41-25 

Red,    .... 

13,000 

36-875 

352-5 

White, 

11,800 

34-625 

340-8 

Yellow, 

13,000 

28-812 

451-2 

Va,       .... 

19,200 

Poplar,         .... 

7,000 

23-937 

292-4 

White,     . 

33-062 

Redwood,  Cal,     . 

10,833 

Spruce,         .... 
Sycamore,    .... 
Tamarack,   .... 

12,400 
13,000 

31-25 
38-937 
23-937 

396-8 
333-8 

Teak,  African,     . 

2l',000 

61-25 

342-8 

„     Indian, 

15,000 

41-062 

365-3 

Walnut,       .... 

41  -937 

„        Black,    . 

16,633 

31-25 

532-2 

,,        Michigan, 
Willow,        .... 

17,500 

13,000 

36:562 

355-5 

ARTIFICIAL   AND   NATURAL    FLIGHT. 


members  are  once  made,  they  are  exceedingly  strong  and 
stiff.     Fig.  46  shows  sections  of  the  struts,  and  these  may 


Fig.  45. — System  of  splicing  and  building  up  wooden  members.  When 
they  have  to  be  curved  and  to  keep  their  shape,  they  should  be  bent 
at  the  curve  at  the  time  of  being  glued  together,  and  joined  in  the 
middle  as  at  d. 

be  made  of  either  straight-grained  Honduras  mahogany  or 
of   lance   wood ;   either  answers   the  purpose   very   well, 


Section  of  Middle  of  Strut. 


Section,  of  Ends  of  Strut. 

Fig.  46.— Cross-section  of  struts. 


HINTS    AS    TO    THE    BUILDING    OF    FLYING    MACHINES. 


because  being  very  strong  and  straight- 
grained,  permits  the  struts  to  be  made 
of  such  a  shape  and  size  as  to  offer 
very  little  resistance  in  cutting  their 
way  through  the  air.  The  framework 
of  the  aeroplane  unless  carefully  de- 
signed will  offer  great  resistance  to 
being  driven  through  the  air.  Suppose 
that  the  bottom  member  of  the  truss 
(Fig.  47)  is  straight,  and  the  top  one 
curved  in  the  direction  shown ;  no 
matter  how  taut  the  cloth  may  be 
drawn,  the  pressure  of  the  air  will 
cause  it  to  bag  upwards  between  the 
different  trusses,  so  as  to  present  very 
nearly  the  correct  curve  which  is 
necessary  to  produce  the  maximum 
lifting  effect,  and  without  offering  too 
much  resistance  to  the  air ;  however, 
one  must  not  forget  for  a  single  moment 
that  the  air  flows  over  both  sides  of 
the  aeroplane.  When  the  aeroplane  is 
made  very  thick  in  the  middle  and 
sharp  at  the  edges  (Fig.  48),  with  the 
bottom  side  dead  level,  it  produces  a 
decided  lifting  effect  no  matter  which 
way  it  is  being  propelled  through  the 
air.  This  is  not  because  the  bottom 
side  produces  any  lifting  effect  of  itself, 
but  because  the  air  running  over  the 
top  follows  the  surface.  The  aeroplane 
encounters  air  which  is  not  moving  at 
all.  The  air  is  first  moved  upwards 
slightly,  but  it  also  has  to  run  down 
the  incline  to  the  rear  edge  of  the 
aeroplane,  so  that,  when  it  is  discharged, 
it  has  a  decided  downward  trend ; 
therefore,  the  air  passing  over  the  top 
side  instead  of  under  the  bottom  side, 
produces  the  lifting  effect,  showing 
that  the  top  side  of  an  aeroplane  as 
well  as  the  lower  side  should  be  con- 
sidered. The  top  side  should,  therefore, 
be  free  from  all  obstructions. 


88  ARTIFICIAL   AND    NATURAL    FLIGHT. 

The  top  of  the  aeroplane  as  well  as  the  bottom  should  be 
covered  with  some  light  material,  if  the  very  best  results 
are  to  be  obtained.  In  another  chapter  I  have  shown  a 
form  of  fabric-covered  aeroplane,  made  by  myself,  that  was 
not  distorted  in  the  least  by  the  air  pressure,  and  produced 
just  as  good  effects  as  it  would  have  done  if  it  had  been 
carefully  carved  out  of  a  piece  of  wood.  On  more  than  one 
occasion  Lord  Kelvin  came  to  my  place ;  he  said  that  my 
workshop  was  a  perfect  museum  of  invention.  At  the 
Oxford  Meeting  of  the  British  Association  for  the  Advance- 
ment of  Science,  Lord  Salisbury  in  the  chair,  I  was  much 
gratified  when  Lord  Kelvin  said  that  he  had  examined  my 
work,  and  found  that  it  was  beautifully  designed  and 
splendidly  executed.  He  complimented  me  very  highly 
indeed.  While  at  my  place,  he  said  that  the  most  ingeni- 
ous thing  that  he  had  seen  was  the  way  I  had  prevented 
my  aeroplanes  from  being  distorted  by  the  air.  He  spoke 
of  this  several  times  with  great  admiration,  and,  I  think,  if 
the  fabric-covered  aeroplane  is  to  be  used  at  all,  that  my 
particular  system  will  be  found  altogether  the  best. 


Fig.  48.  — The  paradox  aeroplane  that  lifts  no  matter  in  which 
direction  it  is  being  driven. 

Regarding  the  motors  now  being  employed,  I  think 
that  there  is  still  room  for  a  great  deal  of  improvement 
in  the  direction  of  greater  lightness,  higher  efficiency 
and  reliability.  At  the  present  time,  flying  machine 
motors  have  such  small  cylinders,  the  rotation  is  so  rapid, 
and  the  cooling  appliances  so  imperfect,  that  the  engine 
soon  becomes  intensely  heated,  and  then  its  efficiency 
is  said  to  fall  off  about  40  or  50  per  cent.,  some  say  even 
60  per  cent.  This  is  probably  on  account  of  the  high 
temperature  of  the  cylinder,  piston,  and  air  inlet.  The 
heat  expands  the  air  as  it  enters,  so  that  the  actual  weight 
of  air  in  the  cylinder  is  greatly  reduced,  and  the  engine 
power  reduced  in  a  corresponding  degree.  There  is  no 
trouble  about  cooling  the  motor,  and  a  condenser  of  high 
efficiency  may  be  made  that  will  cool  the  water  perfectly, 
and,  at  the  same  time,  lift  a  good  deal  more  than  its 
own  weight.  All  the  conditions  are  favourable  for  using 


HINTS   AS   TO   THE    BUILDING   OF    FLYING   MACHINES.  89 


90  ARTIFICIAL   AND    NATURAL   FLIGHT. 

a    very    effective    atmospheric    condenser    (see    Figs.    30 


may  be  considered  as  2400  times  as  efficient  as 
air,  volume  for  volume,  in  condensing  steam.  When  a 
condenser  is  made  for  the  purpose  of  using  water  as  a 
cooling  agent,  a  large  number  of  small  tubes  may  be  closely 
grouped  together  in  a  box,  and  the  water  pumped  in  at  one 
end  of  the  box  and  discharged  at  the  other  end  through 
relatively  small  openings  ;  but  when  air  is  employed,  the 
tubes  or  condensing  surfaces  must  be  widely  distributed,  so 
that  a  very  large  amount  of  air  is  encountered,  and  air 
which  has  struck  one  tube  and  become  heated  must  never 
touch  a  second  tube  (see  Figs.  30  and  31,  also  Appendix). 


Fig.  60. — Section  showing  the  Antoinette  motor,  such  as  used  in 
the  Farraan  and  De  la  Grange  machines. 

Fig.  51  shows  a  pneumatic  buffer  which  I  have  designed, 
in  which  a,  a,  is  a  steel  tube  highly  polished  on  the  inside  ; 
b,  a  nozzle  for  connecting  the  air-pump,  which  is  of  the 
bicycle  variety;  c,  a  nipple  to  which  is  attached  a  strong 
india-rubber  bulb ;  d,  a  piston  which  is  made  air-tight  by 
a  leather  cup ;  and  /,  the  connection  to  the  lever  carrying 
the  wheels  on  which  the  machine  runs.  While  the  machine 
is  at  a  state  of  rest  on  the  ground,  the  piston-rod  d,  is  run 
out  to  its  full  extent,  and  supports  the  weight  of  the 
machine — the  pressure  being  about  150  Ibs.  to  the  square 
inch.  When,  however,  the  machine  comes  violently  down 


HINTS    AS   TO   THE    BUILDING    OP    FLYING    MACHINES. 


to  the  earth,  the  piston  is  pushed 
inward,  compressing  the  air,  and  by 
the  time  it  has  travelled,  say,  one- 
half  the  stroke,  the  air  pressure  will 
have  mounted  to  300  Ibs.  to  the 
square  inch.  At  this  point,  the 
rubber  bulb  c,  ought  to  burst  and 
allow  the  compressed  air  to  escape 
under  a  high  pressure.  Air  escaping 
through  a  relatively  small  hole  ab- 
sorbs the  momentum  of  the  descent 
and  brings  the  machine  to  a  state 
of  rest  without  a  destructive  shock. 
It  is,  of  course,  necessary  for  the 
navigator  to  select  a  broad  and  level 
field  for  descent,  and  then  to  ap- 
proach it  from  the  leeward  and  slow 
up  his  machine  as  near  the  ground 
as  possible,  tilting  the  forward  end 
upwards  in  order  to  arrest  its  for- 
ward motion,  and  touching  the 
ground  while  still  moving  against 
the  wind  at  a  fairly  high  velocity. 
If  all  these  points  are  studied,  and 
well  carried  out,  very  little  danger 
will  result;  then,  again,  the  aero- 
planes b,  b,  and  the  forward  rudder 
d  (Fig.  41),  should  be  so  arranged 
that,  in  case  of  an  accident,  their 
outward  sides  may  be  instantly 
turned  upwards,  in  such  a  manner 
as  to  prevent  the  machine  from 
plunging,  and  keep  it  on  an  even 
keel  while  the  engines  are  not 
running. 


ct 


Fig.  51.— Pneumatic  buffer 
— a,  a,  cylinder;  b,  at- 
tachment for  pumping 
up ;  c,  air  outlet,  covered 
with  a  rubber  thimble 
made  to  burst  under  about 
300  Ibs.  pressure  ;  d,  the 
piston. 


92  ARTIFICIAL   AND    NATURAL    FLIGHT. 


STEERING   BY    MEANS    OF   A    GYROSCOPE. 

A  ship  at  sea  has  only  to  be  steered  in  a  horizontal 
direction;  the  water  in  which  it  is  floated  assures  its 
stability  in  a  vertical  direction  ;  but  when  a  flying  machine 
is  once  launched  in  the  air,  it  has  to  be  steered  in  two 
directions — that  is,  the  vertical  and  the  horizontal.  More- 
over, it  is  constantly  encountering  air  currents  that  are 
moving  with  a  much  higher  velocity  than  any  water 
currents  that  have  ever  to  be  encountered.  It  is,  therefore, 
evident  that,  as  far  as  vertical  steering  is  concerned,  it 
should  be  automatic.  Some  have  suggested  shifting 
weights,  flowing  mercury,  and  swinging  pendulums;  but 
none  of  these  is  of  the  least  value,  on  account  of  the 
swaying  action  which  always  has  to  be  encountered.  A 
pendulum  could  not  be  depended  upon  for  working 
machinery  on  board  a  ship,  and  the  same  laws  apply  to 
an  airship.  We  have  but  one  means  at  our  disposal,  and 
that  is  the  gyroscope.  When  a  gyroscope  is  spun  at  a  very 
high  velocity  on  a  vertical  axis,  with  the  point  of  support 
very  much  above  the  center  of  gyration,  it  has  a  tendency 
to  maintain  a  vertical  axis ;  a  horizontal  or  swinging  motion 
of  its  support  will  not  cause  it  to  swing  like  a  pendulum. 
It  therefore  becomes  possible  by  its  use  to  maintain  an  air- 
ship on  an  even  keel.  In  a  steam  steering  apparatus,  such 
as  is  used  on  shipboard,  it  is  not  sufficient  to  apply  steam- 
power  to  move  the  rudders,  unless  some  means  are  pro- 
vided whereby  the  movement  of  the  rudder  closes  off  the 
steam,  otherwise  the  rudder  might  continue  to  travel  after 
the  effect  had  been  produced,  and  ultimately  be  broken ; 
and  so  it  is  with  steering  a  flying  machine  in  a  vertical 
direction.  Whenever  the  fore  and  aft  rudders  respond  to 
the  action  of  the  gyroscope  and  are  set  in  motion,  they 
must  at  once  commence  to  shut  off  the  power  that  works 
them,  otherwise  they  would  continue  to  travel.  In  the 
photograph  (Fig.  52)  I  have  shown  an  apparatus  which  I 
constructed  at  Baldwyn's  Park.  It  will  be  seen  that  the 
gyroscope  is  enclosed  in  a  metal  case  ;  a  tangent  screw,  just 
above  the  case,  rotates  a  pointer  around  a  small  disc,  which 
admits  of  the  speed  of  the  gyroscope  being  observed. 
Steam  is  admitted  through  a  universal  joint,  descends 
through  the  shaft  and  escapes  through  a  series  of  small 
openings  placed  at  a  tangent,  so  as  to  give  rotation  to  the 


STEERING    BY    MEANS    OF   A   GYROSCOPE.  93 

wheel  after  the  manner  of  a  Barker's  mill.  The  casing 
about  the  rotating  wheel  is  extremely  light  as  relates  to  the 
wheel,  so  that,  when  the  gyroscope  is  once  spun  on  a 
vertical  axis,  the  rest  of  the  apparatus  may  be  tilted  in  any 
direction,  while  the  gyroscope  and  its  attachments  maintain 
a  vertical  axis.  The  gyroscope  and  its  attachments  are 
suspended  from  a  long  steel  tube,  which  in  reality  is  a 
steam  cylinder.  The  sleeve  which  supports  the  gyroscope 
moves  freely  in  a  longitudinal  direction,  and  the  whole  is 
held  in  position  by  a  triple-threaded  screw  on  the  small 
tube  above  the  cylinder.  The  steam  is  admitted  through 
a  piston  value  operated  by  a  species  of  link  motion,  as 
shown.  The  piston-rod  extends  to  each  end  of  the  cylinder, 
and  regulates  the  rudders  by  pulling  a  small  wire  rope,  the 
travel  of  the  piston  being  about  8  feet.  At  the  end  of  the 
cylinder  (not  shown)  the  piston-rod  is  provided  with  an 
arm  and  a  nut  which  engages  the  small  top  tube — this  tube 
being  provided  with  a  long  spiral — so  that,  as  the  piston 
moves,  the  top  tube  is  rotated,  and  thereby  slides  the 
gyroscope's  support,  and  changes  its  position  as  relates  to 
the  piston  valve.  It  will,  therefore,  be  seen  that  the  action 
is  the  same  as  with  the  common  steam  steering  gear  used 
on  shipboard.  A  little  adjusting  screw  at  the  right  hand  of 
the  print  is  shown.  The  upward  projecting  arm  of  the  bell 
crank  lever  is  for  the  purpose  of  attaching  the  wooden 
handle,  making  it  possible  to  move  the  connecting-rod 
instantly  into  a  position  where  the  steam  piston  will  move 
the  rudders  into  the  position  shown  (Fig.  56). 

I  copy  the  following  from  a  description  which  I  wrote 
of  this  apparatus  at  the  time : — 

"  GYROSCOPE  APPARATUS  FOR  AUTOMATICALLY  STEERING 
MACHINE  IN  A  VERTICAL  DIRECTION. 

"  This  apparatus  consists  of  a  long  steam  cylinder  which 
is  provided  with  a  piston,  the  piston-rod  extending  beyond 
the  cylinder  at  each  end ;  the  ropes  working  the  fore  and 
aft  rudders  are  attached  to  the  ends  of  this  piston-rod,  and 
steam  is  supplied  through  an  equilibrium  valve.  The 
gyroscope  is  contained  in  a  gunmetal  case,  and  is  driven  by 
a  jet  of  steam  entering  through  the  trunnions.  When  the 
gyroscope  is  spinning  at  a  high  velocity,  the  casing  holding 
it  becomes  very  rigid  and  is  not  easily  moved  from  its 


94 


ARTIFICIAL   AND    NATURAL    FLIGHT. 


vertical  position.  If  the  machine  rears  or  pitches,  the 
cylinder  and  valve  are  moved  with  the  machine  while 
the  gyroscope  remains  in  a  vertical  position.  This  causes 
the  steam  valve  to  be  moved  so  as  to  admit  steam  into  the 
cylinder  and  move  the  piston  in  the  proper  direction  to 
instantly  bring  the  machine  back  into  its  normal  position. 
As  the  fore  and  aft  rudders  are  moved,  the  long  tubular 
shaft  immediately  over  the  steam  cylinder  is  rotated  in  such 
a  manner  as  to  move  the  whole  gyroscope  in  the  proper 
direction  to  close  off  the  steam.  The  apparatus  may  be 


Fig.  52. — Gyroscope,  used  for  the  control  of  the  fore  and  aft  horizontal 
rudders,  thus  keeping  the  machine  on  an  even  keel  while  in  the  air. 

made  to  regulate  at  any  angle  by  adjusting  the  screw 
which  regulates  the  position  of  the  tubular  shaft.  The  link 
that  suspends  the  end  of  the  steam  valve  connecting-rod  is 
supported  by  a  bell  crank  lever,  and  while  the  machine  is 
moving  ahead,  the  lever  occupies  the  position  shown  in  the 
photograph  (Fig.  52) ;  but  if  the  machinery  and  engine 
stop,  the  bell  crank  lever  may  be  moved  so  as  to  throw  the 
connecting-rod  below  the  centre,  when  the  steam  will  move 
the  piston  in  the  proper  direction  to  throw  both  the  rudders 
into  the  falling  position,  as  shown  in  Fig.  56. 


STEERING   BY    MEANS    OF   A   GYROSCOPE. 


95 


ARTIFICIAL   AND    NATURAL    FLIGHT. 


STEERING   BY    MEANS    OF   A   GYROSCOPE.  97 

§ 
I 


/         3 


II 

If 
rs 


|| 


11 


98 


ARTIFICIAL    AND    NATURAL    FLIGHT. 


CHAPTER  VII. 
THE   SHAPE  AND  EFFICIENCY    OF  AEROPLANES. 

IN    Prof.    Langley's    lifetime,   we    had    many   discussions 
regarding  the  width  and  shape  of  aeroplanes.    The  Professor 
had  made  many  experiments  with  very  small  and  narrow 
planes,  and   was  extremely  anxious  to  obtain  some  data 
regarding  the  effect  that  would  be  produced  by  making  the 
planes  of  greater   width.     He  admitted  that  by  putting 
some  two  or  three  aeroplanes  tandem,  and  all  at  the  same 
angle,  the  front  aeroplane  a  (Fig.  57),  would  lift  a  great 
deal  more  than  b,  and  that  c,  would  lift  still  less.     He 
suggested  the  arrangement  shown  at  a',  b',  c',  in  which  b'  is 
set  at  such  an  angle  as  to  give  as  much  additional  accelera- 
tion to  the  air  as  it  had  received  in  the  first  instance  by 
passing  under  a',  and   that  c,  should   also   increase   the 
acceleration  to  the  same  extent.     With  this  arrangement, 
the   lifting   effect   of   the   three   aeroplanes   ought   to   be 
the  same,  but  I  did  not  agree  with  this  theory.      It  seemed 
to  me  that  it  would  only  be  true  if  it  dealt  with   the 
volume  of  air  represented  between  j,  and  k,  and  that  he  did 
not  take  into  consideration  the  mass  of  air  between  k,  and  I, 
that  had  to  be  dealt  with,  and  which  would  certainly  have 
some  effect  in  buoying  up  the  stream  of  air,  j,  k.     Prof. 
Langley  admitted  the  truth  of  this,  and  said  that  nothing 
but   experiment   would  demonstrate  what  the  real  facts 
were.      But  it  was  a  matter  which  I  had  to  deal  with.      I 
did  not  like  the  arrangement  a',  b',  c,  as  the  angle  was  so 
sharp,  especially  at  c',  that  a  very  large  screw  thrust  would 
be  necessary.      I  therefore   made   a   compromise   on  this 
system  which  is  shown  at  a",  b",  c".     In  this  case  a",  has  an 
inclination  of   1  in   10,  b"  an  inclination  of  1  in  6,  and 
c"  an  inclination  of  1  in  5.     It  will  be  seen  that  this  form, 
which  is  shown  as  one  aeroplane  at  a"',  b"',  c"',  is  a  very 
good  shape.      It  is  laid  out  by  first  drawing  the  line  c,  d, 
dropping    the    perpendicular    equal   to   one-tenth   of   the 
distance  between  c  and  d,  and  then  drawing  a  straight  line 
from  c,  through  e,  to  /,  where   another  perpendicular  is 


100  ARTIFICIAL    AND    NATURAL    PLIGHT. 

dropped,  and  half  the  distance  between  d  and  e  laid 
off,  and  another  straight  line  drawn  from  e,  through  g,  to  h, 
and  the  perpendicular  h,  i,  laid  off  the  same  as  /,  g.  We 
then  have  four  points,  and  by  drawing  a  curve  through 
these,  we  obtain  the  shape  of  the  aeroplane  shown  above, 
which  is  an  exceedingly  good  one.  This  shape,  however, 
is  only  suitable  for  velocities,  up  to  40  miles  per  hour; 
at  higher  velocities,  the  curvature  would  be  correspondingly 
reduced. 


THE  ACTION  OF  AEROPLANES  AND  THE  POWER 
REQUIRED  EXPRESSED  IN  THE  SIMPLEST 
TERMS. 

IN  designing  aeroplanes  for  flying  machines,  we  should  not 
lose  sight  of  the  fact  that  area  alone  is  not  sufficient.  Our 
planes  must  have  a  certain  length  of  entering  edge — that  is, 
the  length  of  the  front  edge  must  bear  a  certain  relation  to 
the  load  lifted.  An  aeroplane  10  feet  square  will  not  lift 
half  as  much  for  the  energy  consumed  as  one  2  feet  wide 
and  50  feet  long ;  therefore,  we  must  have  our  planes 
as  long  as  possible  from  port  to  starboard.  At  all  speeds  of 
40  miles  per  hour  or  less,  there  should  be  at  least  1  foot  of 
entering  edge  for  every  4  Ibs.  carried.  However,  at  higher 
speeds,  the  length  may  be  reduced  as  the  square  of 
the  speed  increases.  An  aeroplane  1  foot  square  will  not 
lift  one-tenth  as  much  as  one  that  is  1  foot  wide  and  10  feet 
long.  This  is  because  the  air  slips  off  at  the  ends,  but  this 
can  be  prevented  by  a  thin  flange,  or  &  la  Hargrave's  kites. 
An  aeroplane  2  feet  wide  and  100  feet  long  placed  at 
an  angle  of  1  in  10,  and  driven  edgewise  through  the  air  at  a 
velocity  of  40  miles  per  hour,  will  lift  2'5  Ibs.  per  square 
foot.  But  as  we  find  a  plane  100  feet  in  length  too  long  to 
deal  with,  we  may  cut  it  into  two  or  more  pieces  and  place 
them  one  above  the  other— superposed.  This  enables  us  to 
reduce  the  width  of  our  machine  without  reducing  its 
lifting  effect ;  we  still  have  100  feet  of  entering  edge,  we 
still  have  200  feet  of  lifting  surface,  and  we  know  that  each 
foot  will  lift  2-5  Ibs.  at  the  speed  we  propose  to  travel. 
200  x  2-5  =  500 ;  therefore  our  total  lifting  effect  is  500 
Ibs.,  and  the  screw  thrust  required  to  push  our  aeroplane 
through  the  air  is  one-tenth  of  this,  because  the  angle  above 
the  horizontal  is  ]  in  10.  We,  therefore,  divide  what  Prof. 


THE   ACTION    OP   AEROPLANES.  101 

Langley  has  so  aptly  called  the  "lift"  by  10  ;  —  =  50. 

It  will  be  understood  that  the  vertical  component  is  the 
lift,  and  the  horizontal  component  the  drift,  the  expression 
"  drift "  also  being  a  term  first  applied  by  Prof.  Langley. 
Our  proposed  speed  is  40  miles  per  hour,  or  3,520  feet  in  a 
minute  of  time.  If  we  multiply  the  drift  in  pounds  by  the 
number  of  feet  travelled  in  a  minute  of  time,  and  divide  the 
product  thus  obtained  by  33,000,  we  ascertain  the  H.P. 
required — 

50  x  3,520 
33,000 

It  therefore  takes  5 '33  H.P.  to  carry  a  load  of  500  Ibs.  at  a 
rate  of  40  miles  per  hour,  allowing  nothing  for  screw  slip  or 
atmospheric  resistance  due  to  framework  and  wires.  But 
we  find  we  must  lift  more  than  500  Ibs.,  and  as  we  do  not 
wish  to  make  our  aeroplanes  any  longer,  we  add  to  their 
width  in  a  fore  and  aft  direction — that  is,  we  place  another 
similar  aeroplane,  also  2  feet  wide,  just  aft  of  our  first 
aeroplane.  This  will,  of  course,  have  to  engage  the  air 
discharged  from  the  first,  and  which  is  already  moving 
downwards.  It  is,  therefore,  only  too  evident  that  if  we 
place  it  at  the  same  angle  as  our  first  one — viz.,  1  in  10 — it 
will  not  lift  as  much  as  the  first  aeroplane,  and  we  find  that 
if  we  wish  to  obtain  a  fairly  good  lifting  effect,  it  must  be 
placed  at  an  angle  of  1  in  6.  Under  these  conditions,  the 
screw  thrust  for  this  plane  will  be  £th  part  of  the  lift,  or 
8-88  H.P.  against  5'33  H.P.  with  our  first  aeroplane.  In 
order  to  avoid  confusion,  we  will  call  our  first  plane  a",  our 
second  plane  b",  and  the  third  c",  the  same  as  in  Fig.  57. 
Still  we  are  not  satisfied,  we  want  more  lift,  we  therefore 
add  still  another  aeroplane  as  shown  (c",  Fig.  57).  This 
one  has  to  take  the  air  which  has  already  been  set  in 
motion  by  the  two  preceding  planes  a"  and  b",  so  in  order 
to  get  a  fair  lifting  effect,  we  have  to  place  our  third  plane 
at  the  high  angle  of  1  in  5.  At  this  angle,  our  thrust  has 
to  be  ith  of  the  lifting  effect,  and  the  H.P.  required  is  twice 
as  much  per  pound  carried  as  with  the  plane  a",  where  the 
angle  was  1  in  10;  therefore,  it  will  take  10*66  H.P.  to 
carry  500  Ibs.  As  there  is  no  reason  why  we  should  have 
three  aeroplanes  placed  tandem  where  one  would  answer 
the  purpose  much  better,  we  convert  the  whole  of  them 
into  one,  as  shown  (a",  b'",  c'",  Fig.  57),  and  by  making 


102 


ARTIFICIAL    AND    NATURAL    FLIGHT. 


the  top  side  smooth  and  uniform,  we  get  the  advantage  of 
the  lifting  effect  due  to  the  air  above  the  aeroplane  as  well 
as  below  it.  The  average  H.P.  is  therefore  5'33  +  8'SS  + 


Fig.  57.— Diagram  showing  the  evolution  of  a  wide  aeroplane. 

10-66  -  3  =  8-29  H.P.  for  each  plane,  or  25  H.P.  for  the 
whole,  which  is  at  the  rate  of  60  Ibs.  to  the  H.P.,  all  of 
which  is  used  to  overcome  the  resistance  due  to  the  weight 


THE   ACTION    OP    AEROPLANES.  103 

and  the  inclination  of  the  aeroplanes,  and  which  is  about 
half  the  total  power  required.  We  should  allow  as  much 
more  for  loss  in  screw  slip  and  atmospheric  resistance  due 
to  the  motor,  the  framework,  and  the  wires  of  the  machine. 
If,  however,  the  screw  is  placed  in  the  path  of  the  greatest 
resistance,  it  will  recover  a  portion  of  the  energy  imparted 
to  the  air.  We  shall,  however,  require  a  50  H.P.  motor, 
and  thus  have  30  Ibs.  to  the  H.P. 

From  the  foregoing  it  will  be  seen  that  at  a  speed  of 
40  miles  an  hour,  the  weight  per  H.P.  is  not  very  great.  If  we 
wish  to  make  a  machine  more  efficient,  we  must  resort  to  a 
multitude  of  very  narrow  superposed  planes,  or  sustainers,  as 
Mr.  Philipps  calls  them,  or  we  must  increase  the  speed.  If  an 
aeroplane  will  lift  2*5  Ibs.  per  square  foot  placed  at  an  angle 
of  1  in  10,  and  driven  at  a  velocity  of  40  miles  an  hour,  the 
same  aeroplane  will  lift  1*25  Ibs.  if  placed  at  an  angle  of 
1  in  20,  and  as  the  lifting  effect  varies  as  the  square  of  the 
velocity,  the  same  plane  will  lift  as  much  more  at  60  miles 
per  hour,  as  602  is  greater  than  402 — that  is,  2 '81  Ibs.  per 
square  foot  instead  of  T25  Ibs.  At  this  high  speed,  pro- 
viding that  the  width  of  the  plane  is  not  more  than  3  feet, 
it  need  be  only  slightly  curved  and  have  a  mean  angle  of 
1  in  20. 

An  aeroplane  100  feet  long  and  3  feet  wide  would  have 
300  square  feet  of  lifting  surface,  each  of  which  would  lift 
2-81  Ibs.,  making  the  total  lifting  effect  843  Ibs.  843  -T-  20  = 
42'15,  which  is  the  screw  thrust  that  would  be  necessary  to 
propel  such  a  plane  through  the  air  at  a  velocity  of  60  miles 
per  hour.  60  miles  per  hour  is  5,280  feet  in  a  minute, 
therefore  the  H.P.  required  is  42 15  X  5,280  -=-  33,000  =  67 
H.P.  Dividing  the  total  lifting  effect  843  by  67,  we 
have  843  -r-  67  =  125'8,  the  lift  per  H.P.  If  we  allow  one- 
half  for  loss  in  friction,  screw  slip,  etc.,  we  shall  be  carrying 
a  load  of  843  Ibs.  with  I3'4  H.P.  It  will,  therefore,  be  seen 
that  a  velocity  of  60  miles  an  hour  is  much  more  economical 
in  power  than  the  comparatively  low  velocity  of  40  miles 
an  hour;  moreover,  it  permits  of  a  considerable  reduction  in 
the  size  and  weight  of  the  machine,  and  this  diminishes  the 
atmospheric  resistance. 


104 


ARTIFICIAL   AND    NATURAL    FLIGHT. 


HORIZONTAL  LIHE 


Fig.  58.— In  a  recently  published  mathematical  treatise  on  Aerodynamics, 
an  illustration  is  shown,  representing  the  path  that  the  air  takes  on  en- 
countering a  rapidly  moving  curved  aeroplane.  It  will  be  observed  that 
the  air  appears  to  be  attracted  upwards  before  the  aeroplane  reaches 
it,  exactly  as  iron  filings  would  be  attracted  by  a  magnet,  and  that 
the  air  over  the  top  of  the  aeroplane  is  thrown  off  at  a  tangent,  pro- 
ducing a  strong  eddying  effect  at  the  top  and  rear.  Just  why  the  air 
rises  up  before  the  aeroplane  reaches  it  is  not  plain,  and  as  nothing 
could  be  further  from  the  facts,  mathematical  formulae  founded  on 
such  a  mistaken  hypothesis  can  be  of  but  little  value  to  the  serious 
experimenter  on  flying  machines. 


Fig.  59.— An  illustration  from  another  scientific  publication  also  on  the 
Dynamics  of  Flight.  It  will  be  observed  that  the  air  in  striking  the 
underneath  side  of  the  aeroplane  is  divided  into  two  streams,  a 
portion  of  it  flowing  backwards  and  over  the  top  of  the  edge  of  the 
aeroplane  where  it  becomes  compressed.  An  eddy  is  formed  on  the 
back  and  top  of  the  aeroplane,  and  the  air  immediately  aft  the  aero- 
plane is  neither  rising  nor  falling.  Just  how  these  mathematicians 
reason  out  that  the  air  in  striking  the  front  of  the  aeroplane  would 
jump  backwards  and  climb  up  over  the  top  and  leading  edge  against 
the  wind  pressure  is  not  clear. 


THE    ACTION    OF   AEROPLANES. 


105 


Fig.  60. — This  shows  another  illustration  from  the  same  mathematical 
work,  and  represents  the  direction  which  the  air  is  supposed  to  take 
on  striking  a  flat  aeroplane.  With  this,  the  air  is  also  divided,  a 
portion  moving  forward  and  over  the  top  of  the  aeroplane  where  it  is 
compressed,  leaving  a  large  eddy  in  the  rear,  and,  as  the  dotted  lines 
at  the  back  of  the  aeroplane  are  horizontal,  it  appears  that  the  air  is 
not  forced  downwards  by  its  passage.  Here,  again,  fornmla  founded 
on  such  hypothesis  is  misleading  in  the  extreme. 


Fig.  61. — This  shows  the  shape  and  the  practical  angle  of  an  aeroplane. 
This  angle  is  1  in  10,  and  it  will  be  observed  that  the  air  follows  both 
the  upper  and  the  lower  surface,  and  that  it  leaves  the  plane  in  a 
direction  which  is  the  resultant  of  the  top  and  bottom  angle. 


106 


ARTIFICIAL    AND    NATURAL    PLIGHT. 


#O*,ZONTAI.  LINK 


Fig.  62. — This  shows  an  aeroplane  of  great  thickness,  placed  at  the 
highest  angle  that  will  ever  be  used — 1  in  4 — and  even  with  this  the 
air  follows  the  upper  and  lower  surfaces.  No  eddies  are  formed,  and 
the  direction  that  the  air  takes  after  leaving  the  aeroplane  is  the 
resultant  of  the  top  and  bottom  angles. 


Fig.  68. — Section  of  a  screw  blade  having  a  rib  on  the  back.      The  resist- 
ance caused  by  this  rib  is  erroneously  supposed  to  be  skin  friction. 


THE    ACTION    OF   AEROPLANES. 


Fig.  64. — Shows  a  flat  aeroplane  placed  at  an  angle  of  45°,  an  angle  which 
will  never  be  used  in  practical  flight,  but  at  this  angle  the  momentum 
of  the  approaching  air  and  the  energy  necessary  to  give  it  an  acceler- 
ation sufficiently  great  to  make  it  follow  the  back  of  the  aeroplane 
are  equal,  and  at  this  point,  the  wind  may  either  follow  the  surface  or 
not.  Sometimes  it  does  and  sometimes  it  does  not.  See  experiments 
with  screws. 


Fig.  65. — The  aeroplane  here  shown  is  a  mathematical  paradox.  This 
aeroplane  lifts,  no  matter  in  which  direction  it  is  driven.  It 
encounters  air  which  is  stationary  and  leaves  it  with  a  downward 
trend;  therefore  it  must  lift.  However,  if  we  remove  the  section  b, 
and  only  subject  a  to  the  blast,  as  shown  at  Fig.  66,  no  lifting  effect 
is  produced.  On  the  contrary,  the  air  has  a  tendency  to  press  a, 
downwards.  The  path  which  the  air  takes  is  clearly  shown ;  this  is 
most  important,  as  it  shows  that  the  shape  of  the  top  side  is  a  factor 
which  has  to  be  considered.  All  the  lifting  effect  in  this  case  is  pro- 
duced by  the  top  side. 


108 


ARTIFICIAL    AND    NATURAL    FLIGHT. 


Fig.  67. — In  this  drawing  a  represents  an  aeroplane,  or  a  bird's  wing. 
Suppose  that  the  wind  is  blowing  in  the  direction  of  the  arrows ;  the 
real  path  of  the  bird  as  relates  to  the  air  is  from  i  to  j, — that  is,  the 
bird  is  falling  as  relates  to  the  air  although  moving  on  the  line  c,  d, 
against  the  wind.  In  some  cases,  a  bird  is  able  to  travel  along  the  line 
g,  h,  instead  of  in  a  horizontal  direction,  thus  rising  and  apparently 
flying  into  the  teeth  of  the  wind  at  the  same  time. 


SOME    RECENT    MACHINES.  109 


SOME   RECENT    MACHINES. 

Professor  S.  P.  Langley,  .of  the  Smithsonian  Institute, 
Washington,  D.C.,  made  a  small  flying  model  in  1896. 
This,  however,  only  weighed  a  few  pounds ;  but  as  it  did 
actually  fly  and  balance  itself  in  the  air,  the  experiment 
was  of  great  importance,  as  it  demonstrated  that  it  was 
possible  to  make  a  machine  with  aeroplanes  so  adjusted 
as  to  steer  itself  automatically  in  a  horizontal  direction.  In 
order  to  arrive  at  this  result,  an  innumerable  number  of 
trials  were  made,  and  it  was  only  after  months  of  careful 
and  patient  work  that  the  Professor  and  his  assistants 
succeeded  in  making  the  model  fly  in  a  horizontal  direction 
without  rearing  up  in  front,  and  then  pitching  backwards, 
or  plunging  while  moving  forward. 

The  Wright  Brothers  of  Dayton,  Ohio,  U.S.A.,  often 
referred  to  as  "  the  mysterious  Wrights,"  commenced 
experimental  work  many  years  ago.  The  first  few  years 
were  devoted  to  making  gliding  machines,  and  it  appears 
that  they  attained  about  the  same  degree  of  success  as  many 
others  who  were  experimenting  on  the  same  lines  at  the 
same  time ;  but  they  were  not  satisfied  with  mere  gliding 
machines,  and  so  turned  their  attention  in  the  direction  of 
motors.  After  some  years  of  experimental  work,  they 
applied  their  motor  to  one  of  their  large  gliding  machines, 
and  it  is  said  that  with  this  first  machine  they  actually 
succeeded  in  flying  short  distances.  Later  on,  however, 
with  a  more  perfect  machine,  they  claim  to  have  made 
many  flights,  amongst  which  I  will  mention  three :  12  miles 
in  20  minutes,  on  September  29th,  1905 ;  2075  miles  in  33 
minutes,  on  October  4th  ;  and  24r2  miles  in  38  minutes,  on 
October  5th  of  the  same  year.  As  there  seems  to  be  much 
doubt  regarding  these  alleged  flights,  we  cannot  refer  to 
them  as  facts  until  the  Wright  Brothers  condescend  to  show 
their  machine  and  make  a  flight  in  the  presence  of  others  ; 
nevertheless,  I  think  we  are  justified  in  assuming  that  they 
have  met  with  a  certain  degree  of  success  which  may  or 
may  not  be  equal  to  the  achievments  of  Messrs  Farman  and 
De  la  Grange.  It  is  interesting  to  note  in  this  connection 
that  all  flying  machines  that  have  met  with  any  success 
have  been  made  on  the  same  lines ;  all  have  superposed 
aeroplanes,  all  have  fore  and  aft  horizontal  rudders,  and  all 
are  propelled  with  screws ;  and  in  this  respect  they  do  not 


HO  ARTIFICIAL   AND    NATURAL    FLIGHT. 

differ  from  the  large  machine  that  I  made  at  Baldwyn's 
Park  many  years  ago.  I  have  seen  both  the  Farman  and 
the  De  la  Grange  machines;  they  seem  to  be  about  the  same 
in  size  and  design,  and  what  is  true  of  one  is  equally  true 
of  the  other  ;  I  will,  therefore,  only  describe  the  one  that 
seems  to  have  done  the  best— the  De  la  Grange.  The  general 
design  of  this  machine  is  clearly  shown  in  the  illustrations 
(Figs.  68  and  69).  The  dimensions  are  as  follows  :  The  two 
main  aeroplanes  are  32'8  feet  long  and  4'9  feet  wide ;  the 
tail  or  after  rudder  is  made  in  the  form  of  a  Hargraves'  box 
kite,  the  top  and  bottom  sides  of  the  box  being  curved  and 
covered  with  balloon  fabric,  thus  forming  aeroplanes.  This 
box  is  9'84  feet  long  from  port  to  starboard,  and  6'56  feet 
wide  in  a  fore  and  aft  direction.  The  diameter  of  the  screw 
is  7'2  feet  and  it  has  a  mean  pitch  of  57  feet.  The  screw 
blades  are  two  in  number  and  are  extremely  small,  being 
only  6'3  inches  wide  at  the  outer  end  and  3'15  inches  at 
the  inner  end,  their  length  being  21  feet.  The  space 
between  the  fore  and  aft  aeroplanes  is  4'9  feet.  The  total 
weight  is  about  1,000  Ibs.  with  one  man  on  board.  The 
speed  of  this  machine  through  the  air  is  not  known  with 
any  degree  of  certainty  ;  it  is,  however,  estimated  to  be 
32  to  40  miles  per  hour.  When  the  screw  is  making 
1,100  revolutions  per  minute,  the  motor  is  said  to 
develop  50  H.P. 

In  the  following  calculations,  I  have  assumed  that  the 
machine  has  the  higher  speed — 40  miles  per  hour.  I  have 
been  quite  unable  to  obtain  any  reliable  data  regarding  the 
angle  at  which  the  aeroplanes  are  set,  but  it  would  appear 
that  the  angle  is  about  1  in  10.  The  total  area  of  the  two 
main  aeroplanes  is  321'4  square  feet.  A  certain  portion  of 
the  lower  main  aeroplane  is  cut  away,  but  this  is  com- 
pensated for  by  the  forward  horizontal  rudder  placed  in  the 
gap  thus  formed.  The  two  rear  aeroplanes  forming  the  tail 
of  the  machine  have  an  area  of  128-57  square  feet.  The 
area  of  all  the  areoplanes  is,  therefore,  450  square  feet.  As 
the  weight  of  the  machine  is  1,000  Ibs.,  the  lift  per  square 
foot  is  2'2  Ibs.  Assuming  that  the  angle  of  the  aeroplanes 
is  1  in  10,  the  screw  thrust  would  be  100  Ibs.,  providing, 
however,  that  the  aeroplanes  were  perfect  and  no  friction 
of  any  kind  was  encountered.  Forty  miles  per  hour  is 
at  the  rate  of  3,520  feet  in  a  minute  of  time,  therefore, 

=  10'66  KR     K  We  all°W  another  10  H'R  for 


SOME    RECENT   MACHINES. 


Ill 


atmospheric  resistance  due  to  the  motor,  the  man,  and  the 
framework  of  the  machine,  it  would  require  20'66  H.P.  to 


Fig.  68. — The  De  la  Grange  machine  on  the  ground  and  about  to  make 
a  flight. 


Fig.  69.— The  De  la  Grange  machine  in  full  flight  and  very  near  the 
ground. 

propel  the  machine  through  the  air  at  the  rate  of  40  miles 
per  hour.  If  the  motor  actually  develops  50  H.P.,  29  H.P. 
will  be  consumed  in  screw  slip  and  overcoming  the  re- 


112 


ARTIFICIAL    AND    NATURAL    FLIGHT. 


sistance  due  to  the  imperfect  shape  of  the  screw.  The 
blades  of  the  De  la  Grange  screw  propeller  are  extremely 
small,  and  the  waste  of  energy  is,  therefore,  correspondingly 
great — their  projected  area  being  only  1*6  square  feet  for 
both  blades.  Allowing  200  Ibs.  for  screw  thrust,  we  have 

200 
the  following:    — — -  =  125  Ibs.  pressure  per  square  foot  on 

1'bO 

the  blades.  If  we  multiply  the  pitch  of  the  screw  in  feet 
by  the  number  of  revolutions  per  minute,  we  find  that  if  it 
were  travelling  in  a  solid  nut  it  would  advance  over  70 
miles  an  hour.  By  the  Eiffel  tower  formula  P  =  O'OOS  V2, 
a  wind  blowing  at  a  velocity  of  70  miles  per  hour  produces 
a  pressure  of  14'7  Ibs.  per  square  foot  on  a  normal  plane  ; 
therefore,  assuming  that  the  projected  area  of  the  screw 


Fig.  70. — Farman's  machine  in  flight. 

blades  is  1*6,  we  have  1/6  x  147  =  23'52  Ibs.,  which  is  only 
one-fifth  part  of  what  the  pressure  really  is  when  the 
screws  are  making  1,100  turns  a  minute.  It  is  interesting 
to  note  that  the  ends  of  the  screw  blades  travel  at  a  velocity 
of  414  feet  per  second,  which  is  about  one-half  the  velocity 
of  a  cannon  ball  fired  from  an  old-fashioned  smooth  bore. 

A  flying  machine  has,  of  course,  to  be  steered  in  two 
directions  at  the  same  time — the  vertical  and  the  horizontal. 
In  the  Farman  and  De  la  Grange  machines,  the  horizontal 
steering  is  effected  by  a  small  windlass  provided  with  a 
hand  wheel,  the  same  as  on  a  steam  launch,  and  the  vertical 
steering  is  effected  by  a  longitudinal  motion  of  the  shaft  of 
the  same  windlass.  As  the  length  of  the  machine  is  not 
very  great,  it  requires  very  close  attention  on  the  part  of 
the  man  at  the  helm  to  keep  it  on  an  even  keel;  if  one  is 


SOME    RECENT    MACHINES. 


113 


not  able  to  think  and  act  quickly,  disaster  is  certain.     On 
one  occasion,  the  man  at  the  wheel  pushed  the  shaft  of  the 


Fig.  71. — Bleriot's  machine.  This  machine  raised  itself  from  the  ground, 
but  as  the  centre  of  gravity  was  very  little,  if  any,  above  the  centre 
of  lifting  effect,  it  turned  completely  over  in  the  air. 


Fig.  72. — Santos  Dumont's  flying  machine. 

windlass  forward  when  he  should  have  pulled  it  back,  and 
the  result  was  a  plunge  and  serious  damage  to  the  machine  : 

8 


114 


ARTIFICIAL    AND    NATURAL    FLIGHT. 


happily  no  one  was  injured,  though  some  of  the  bystanders 
were  said  to  have  had  very  narrow  escapes.  The  remedy 
for  this  is  to  make  all  hand-steered  machines  of  great 
length,  which  gives  more  time  to  think  and  act ;  or,  still 
better,  to  make  them  automatic  by  the  use  of  a  gyroscope. 

VELOCITY  AND  PRESSURE  OF  THE  WIND. 

THE  pressure  varies  as  the  square  of  the  velocity  or  P  <x  V2.  The  old 
formula  for  wind  blowing  against  a  normal  plane  was  P  =  0'005  x  V2. 
The  latest  or  Eiffel  Tower  formula  gives  a  much  smaller  value,  being 
P  =  0'003  V-,  where  V  represents  the  velocity  in  miles  per  hour,  and  P 
the  pressure  in  pounds  per  square  foot. 


VELOCITY. 

Pressure 
on  a 
Sq.  Foot. 

Character  of  the  Wind. 

Per  Hour. 

Per  Minute. 

Per  Second. 

Miles. 

Feet. 

Feet. 

Lbs. 

1 
2 
3 

88 
176 
264 

1-5 
2-9 
4-4 

•003 
•012 
•027 

Barely  observable. 
j-  Just  perceptible. 

4 

352 

5-9 

•048 

Light  breeze. 

5 

440 

7'3 

•075 

\ 

6 

528 

8-8 

•108 

>  Gentle,  pleasant  wind. 

8 

704 

11-7 

•192 

\ 

10 

880 

14-7 

•3 

Fresh  breeze. 

15 

1,320 

22 

•675 

Brisk  breeze. 

20 

1,760 

29-4 

12 

Stiff  breeze. 

25 

2,200 

36-7 

1-875 

Very  brisk  breeze. 

30 
35 

2,640 
3,080 

44 
51-3 

2-7 
3-675 

|  High  wind. 

40 
45 

3,520 
3,960 

58-7 
66 

.4-8 
6075 

Very  high  wind. 
Gale. 

50 

4,400 

73-4 

7-5 

Storm. 

60 
70 

5,280 
6,160 

88 
102-7 

10-8 
14-7 

j-  Great  storm. 

80 

7,040 

117-2 

19-2 

Hurricane. 

90 
100 

7,920 
8,800 

132 
146-7 

24-3 
30 

i     Tornado. 

110 

9,680 

161-2 

36-3 

120 

10,560 

176 

43-2 

130 
140 

11,440 
12,320 

191 
205-3 

50-7 
58-8 

"  Washoe  zephyrs."  * 

150 

13,200 

220 

67-5 

*  With  apologies  to  Mark  Twain. 


SOME    RECENT    MACHINES. 
A 


115 


Fig.  72a. — Angles  and  degrees  compared.     It  will  be  observed  that 
an  angle  of  1  in  4  is  practically  14°. 

TABLE  OF  EQUIVALENT  INCLINATIONS. 


Rise. 

Sine  of  Angle. 

Angle  in  Degrees. 

1  in  30, 

•0333 

1-91 

1        25,         ... 

•04 

2-29 

1        20,         ... 

•05 

2-87 

1        18,          ... 

•0555 

3-18 

1        16,          ... 

•0625 

3-58 

1        14,          ... 

•0714 

4-09 

1        12,          ... 

•0333 

4-78 

1        10,         ... 

•1 

573 

1          9,         ... 

•1111 

6-38 

1          8,         ... 

•125 

7-18 

1         7,         ... 

•143 

8-22 

1         6,         ... 

•1667 

9-6 

1          5,         ... 

•2 

11-53 

1          4,         ... 

•25 

14-48 

1,3, 

•3333 

19-45 

116 


ARTIFICIAL   AND    NATURAL    FLIGHT. 

TABLE  OF  EQUIVALENT  VELOCITIES. 


Miles 
per  Hour. 

Feet 
per  Second. 

Feet 
per  Minute. 

Metres 
per  Minute. 

Metres 
per  Second. 

1, 

1-5 

88 

26-8 

•447 

2, 

2-9 

176 

53-6 

•894 

3, 

4-4 

264 

80-5 

1-341 

4, 

5-9 

352 

107-3 

1-788 

5, 

7-3 

440 

134-1 

2-235 

6, 

8-8 

528 

160-9 

2-682 

8, 

11-7                   704 

214-6 

3-576 

10,         .         . 

14-7 

880 

268-2 

4-470 

15, 

22 

1,320 

402-3 

6-705 

20, 

29-4 

1,760 

536-4 

8-940 

25,         .        . 

36-7 

2,200 

670-5 

11-176 

30, 

44 

2,640 

804-6 

13-411 

35, 

51-3 

3,080 

938-8 

15-646 

40, 

58-7 

3,520 

1,072-9 

17-881 

45, 

66 

3,960 

1,207 

20-116 

50, 

73-4 

4,400 

1,341-1 

22-352 

60, 

88 

5,280 

1,609-2 

26-822 

70, 

102-7 

6,160 

1,877-5 

31-292 

80, 

117-2 

7,040 

2,145-8 

35-763 

90, 

132 

7,920 

2,414 

40233 

100, 

146-7 

8,800 

2,682-2 

44-704 

110, 

161-2 

9,680 

2,950-2 

49-174 

120, 

176 

10,560 

3,218-4 

53-644 

130,         .         . 

191 

11,440 

3,486-6 

58-115 

140,         .         . 

205-3 

12,320 

3,755-1 

62  '585 

150, 

220 

13,200 

4,023-3 

67-056 

To  convert  feet  per  minute  into  metres  per  second,  multiply  by  -03508. 


SOME    RECENT    MACHINES. 


117 


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118 


ARTIFICIAL   AND    NATURAL    FLIGHT. 


Fig.  726. — When  an  aeroplane  is  driven  through  the  air,  it  encounters 
stationary  air  and  leaves  it  with  a  downward  trend.  With  a  thick 
curved  aeroplane,  as  shown,  the  air  follows  both  the  top  and  the 
bottom  surfaces,  and  the  direction  that  the  air  takes  is  the  resultant 
of  these  two  streams  of  air.  It  will  be  seen  that  the  air  takes  the 
same  direction  that  it  would  take  if  the  plane  were  flat,  and  raised 
from  a  to  c,  which  would  be  substantially  the  same  as  shown  at  /,  h,  g. 
It  has,  however,  been  found  by  actual  experiment  that  the  curved 
plane  is  preferable,  because  the  lifting  effect  is  more  evenly  distri- 
buted, and  the  drift  is  less  in  proportion  to  the  lift. 

O 


Fig.  72c.— Aeroplanes  experimented  with  by  Mr.  Horatio  Philipps.  In 
the  published  account  which  is  before  me,  the  angles  at  which  these 
planes  were  placed  are  not  given,  but,  by  comparing  the  lift  with  the 
drift,  we  may  assume  that  it  was  about  1  in  10.  | 

Fig.  5  seems  to  have  been  the  best  shape,  and  I  find  that  this  plane 
would  have  given  a  lifting  effect  of  2 -2  Ibs.  per  square  foot  at  a  velocity 
of  40  miles  per  hour. 


SOME    RECENT    MACHINES. 


119 


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120 


CHAPTER  VIII. 
BALLOONS. 

As  far  as  the  actual  navigation  of  the  air  is  concerned, 
balloonists  have  had  everything  to  themselves  until  quite 
recently,  but  we  find  that  at  the  present  moment,  experi- 
menters are  dividing  their  attention  about  equally  between 
balloons  or  machines  lighter  than  the  air,  and  true  flying 
machines  or  machines  heavier  than  the  air.  In  all  Nature. 
we  do  not  find  any  bird  or  insect  that  does  not  fly  by 
dynamic  energy  alone,  and  I  do  not  believe  that  the  time 
is  far  distant  when  those  now  advocating  machines  lighter 
than  the  air,  will  join  the  party  advocating  machines  heavier 
than  the  air,  and,  eventually,  balloons  will  be  abandoned 
altogether.  No  matter  from  what  standpoint  we  examine 
the  subject,  the  balloon  is  unsuitable  for  the  service,  and  it  is 
not  susceptible  of  much  improvement.  On  the  other  hand, 
the  flying  machine  is  susceptible  of  a  good  deal  of  improve- 
ment ;  there  is  plenty  of  scope  for  the  employment  of  a 
great  deal  of  skill,  both  mechanical  and  scientific,  for  a  good 
many  years  to  come. 

I  do  not  know  that  I  can  express  myself  better  now 
than  I  did  when  I  wrote  an  article  for  the  Engineering 
Supplement  of  the  Times,  from  which  I  quote  the 
following ; — 

"  The  result  of  recent  experiments  must  have  convinced 
every  thinking  man  that  the  day  of  the  balloon  is  past.  A 
balloon,  from  the  very  nature  of  things,  must  be  extremely 
bulky  and  fragile. 

"  It  has  always  appeared  to  the  writer  that  it  would  be 
absolutely  impossible  to  make  a  dirigible  balloon  that  would 
be  of  any  use,  even  in  a  comparatively  light  wind.  Experi- 
ments have  shown  that  only  a  few  hundred  feet  above  the 
surface  of  the  earth,  the  air  is  nearly  always  moving  at  a 
velocity  of  at  least  15  miles  an  hour,  and  more  than  two- 
thirds  of  the  time  at  a  velocity  considerably  greater  than 
this.  In  order  to  give  a  balloon  sufficient  lifting  power  to 
carry  two  men  and  a  powerful  engine,  it  is  necessary  that 


BALLOONS. 


it  should  be  of  enormous  bulk.  Considered  as  a  whole, 
including  men  and  engine,  it  must  have  a  mean  density 
less  than  the  surrounding  air,  otherwise  it  will  not  rise. 
Therefore,  not  only  is  a  very  large  surface  exposed  to  the 
wind,  but  the  whole  thing  is  so  extremely  light  and  fragile 
as  to  be  completely  at  the  mercy  of  wind  and  weather. 
Take  that  triumph  of  engineering  skill,  the  '  Nulli  Secundus,' 
for  example.  The  gas-bag,  which  was  sausage-shaped  and 
30  feet  in  diameter,  was  a  beautiful  piece  of  workmanship, 
the  whole  thing  being  built  up  of  goldbeater's  skin.  The 
cost  of  this  wonderful  gas-bag  must  have  been  enormous. 
The  whole  construction,  including  the  car,  the  system  of 
suspension,  the  engine  and  propellers,  had  been  well  thought 
out  and  the  work  beautifully  executed  ;  still,  under  these 
most  favourable  conditions,  only  a  slight  shower  of  rain  was 
sufficient  to  neutralise  its  lifting  effect  completely  —  that  is, 
the  gas-bag  and  the  cordage  about  this  so-called  airship 
absorbed  about  400  Ibs.  of  water,  and  this  was  found  to  be 
more  than  sufficient  to  neutralise  completely  the  lifting 
effect.  A  slight  squall  which  followed  entirely  wrecked  the 
whole  thing,  and  it  was  ignominiously  carted  back  to  the 
point  of  departure. 

"  We  now  learn  that  the  War  Office  is  soon  to  produce 
another  airship  similar  to  the  '  Nulli  Secundus,'  but  with  a 
much  greater  capacity  and  a  stronger  engine.  In  the  news- 
paper accounts  it  is  said  that  the  gas-bag  of  this  new  balloon 
would  be  sausage-shaped  and  42  feet  in  diameter,  that  it  is 
to  be  provided  with  an  engine  of  100  horse-power,  which  it 
is  claimed  will  give  to  this  new  production  a  speed  of 
40  miles  an  hour  through  the  air,  so  that,  with  a  wind  of 
20  miles  an  hour,  it  will  still  be  able  to  travel  by  land 
20  miles  an  hour  against  the  wind.  Probably  the  writer  of 
the  article  did  not  consider  the  subject  from  a  mathematical 
point  of  view.  As  the  mathematical  equation  is  an  extremely 
simple  one,  it  is  easily  presented  so  as  to  be  understood  by 
any  one  having  the  least  smattering  of  mathematical  or 
engineering  knowledge.  The  cylindrical  portion  of  the  gas- 
bag is  to  be  42  feet  in  diameter  ;  the  area  of  the  cross-section 
would  therefore  be  1,385  feet.  If  we  take  a  disc  42  feet  in 
diameter  and  erect  it  high  in  the  air  above  a  level  plain, 
and  allow  a  wind  of  40  miles  an  hour,  which  is  the  proposed 
speed  of  the  balloon,  to  blow  against  it,  we  should  find  that 
the  air  pressure  would  be  11,083  Ibs.  —  that  is,  a  wind  blowing 
at  a  velocity  of  40  miles  an  hour  would  produce  a  pressure 


122  ARTIFICIAL   AND    NATURAL   FLIGHT. 

of  8  Ibs.  to  every  square  foot  of  the  disc.*  Conversely,  if  the 
air  were  stationary,  it  would  require  a  push  of  11,083  Ibs.  to 
drive  this  disc  through  the  air  at  the  rate  of  40  miles  an 
hour. 

"  A  speed  of  40  miles  an  hour  is  at  the  rate  of  3,520  feet 
in  a  minute  of  time.  We  therefore  have  two  factors — the 
pounds  of  resistance  encountered,  and  the  distance  through 
which  the  disc  travels  in  one  minute  of  time.  By  multi- 
plying the  total  pounds  of  pressure  on  the  complete  disc  by 
the  number  of  feet  it  has  to  travel  in  one  minute  of  time,  we 
have  the  total  number  of  foot-pounds  required  in  a  minute 
of  time  to  drive  a  disc  42  feet  in  diameter  through  the  air 
at  a  speed  of  40  miles  an  hour.  Dividing  the  product  by 
the  conventional  horse-power  33,000,  we  shall  have  1,181 
horse-power  as  the  energy  required  to  propel  the  disc  through 
the  air.  However,  the  end  of  the  gas-bag  is  not  a  flat  disc, 
but  a  hemisphere,  and  the  resistance  to  drive  a  hemisphere 
through  the  air  is  much  less  than  it  would  be  with  a  normal 
plane  or  flat  disc.  In  the  '  Nulli  Secundus'  we  may  take 
the  coefficient  of  resistance  of  the  machine,  considered  as  a 
whole,  as  0'20— that  is,  that  the  resistance  will  be  one-fifth 
as  much  as  that  of  a  flat  disc.  This,  of  course,  includes  not 
only  the  resistance  of  the  balloon  itself,  but  also  that  of  the 
cordage,  the  car,  the  engine,  and  the  men. 

"Multiplying  1,181  by  the  coefficient  '20,  we  shall  have 
236 ;  therefore,  if  the  new  balloon  were  attached  to  a  long 
steel  wire  and  drawn  by  a  locomotive  through  the  air,  the 
amount  of  work  or  energy  required  would  be  236  horse- 
power— that  is,  if  the  gas-bag  would  stand  being  driven 
through  the  air  at  the  rate  of  40  miles  an  hour,  which  is 
extremely  doubtful.  Under  these  conditions,  the  driving 
wheels  of  the  locomotive  would  not  slip,  and  therefore  no 
waste  of  power  would  result,  but  in  the  dirigible  balloon 
we  have  a  totally  different  state  of  affairs.  The  propelling 
screws  are  very  small  in  proportion  to  the  airship,  and  their 
slip  is  fully  50  per  cent— that  is,  in  order  to  drive  the  ship 
at  the  rate  of  40  miles  an  hour,  the  screws  would  have  to 

*  Haswell  gives  the  pressure  of  the  wind  at  40  miles  an  hour  as  8  Ibs. 
per  square  foot,  and  this  is  said  to  have  been  verified  by  the  United 
btates  Coast  Survey.  Molesworth  makes  it  slightly  less;  but  the  new 
formula,  according  to  most  recent  experiments  (Dr.  Stanton's  experiments 
at  the  National  Physical  Laboratory  and  M.  Eiffel's  at  Eiffel  Tower), 
is  P  =  0-003  V2,  which  would  make  the  pressure  only  4 '8  Ibs.  per  square 
foot,  and  which  would  reduce  the  total  H.P.  required  from  472  to  283, 
where  P  represents  pounds  per  square  foot  and  V  miles  per  hour. 


BALLOONS.  123 

travel  at  least  80  miles  an  hour.  Therefore,  while  236  horse- 
power was  imparted  to  the  ship  in  driving  it  forward,  an 
equal  amount  would  have  to  be  lost  in  slip,  or,  in  other 
words,  in  driving  the  air  rearwards.  It  would,  therefore, 
require  472  horse-power  instead  of  100  to  drive  the  proposed 
new  balloon  through  the  air  at  the  rate  of  40  miles  an  hour. 
"  It  will  be  seen  from  this  calculation  that  the  new 
airship  will  still  be  at  the  mercy  of  the  wind  and 
weather.  Those  who  pin  their  faith  on  the  balloon  as 
the  only  means  of  navigating  the  air  may  dispute  my 
figures.  However,  all  the  factors  in  the  equation  are 
extremely  simple  and  well  known,  and  no  one  can 
dispute  any  of  them  except  the  assumed  coefficient  of 
resistance,  which  is  given  here  as  '20.  The  writer  feels 


Fig.  73.— The  enormous  balloon,  "Ville  de  Paris,"  of  the  French  Govern- 
ment. This  balloon  is  a  beautiful  piece  of  workmanship,  and  is  said  to 
be  the  most  practical  balloon  ever  invented,  not  excepting  the  balloon 
of  Count  Zeppelin.  Some  idea  of  its  size  may  be  obtained  by 
comparing  it  with  the  size  of  the  men  who  are  standing  immediately 
underneath. 

quite  sure  that,  after  careful  experiments  are  made,  it 
will  be  found  that  this  coefficient  is  nearer  '40  than  "20, 
especially  so  at  high  speeds  when  the  air  pressure 
deforms  the  gas-bag.  Only  a  slight  bagging  in  the  front 
end  of  the  balloon  would  run  the  coefficient  up  to  fully  '50, 
and  perhaps  even  more." — Times,  Feb.  26,  1908. 

Since  writing  the  Times  article,  a  considerable  degree  of 
success  has  been  attained  by  Count  Zeppelin.     According 


124  ARTIFICIAL    AND    NATURAL    FLIGHT. 

to  newspaper  accounts,  his  machine  has  a  diameter  of 
about  40  feet,  and  a  length  of  no  less  than  400  feet.  It 
appears  that  this  balloon  consists  of  a  very  light  aluminium 
envelope,  which  is  used  in  order  to  produce  a  smooth 
and  even  surface,  give  rigidity,  and  take  the  place  of 
the  network  employed  in  ordinary  balloons.  It  seems 
that  the  gas  is  carried  in  a  large  number  of  bags  fitted 
in  the  interior  of  this  aluminium  envelope.  However, 
by  getting  a  firm  and  smooth  exterior  and  by  making 
his  apparatus  of  very  great  length  as  relates  to  its 
diameter,  he  has  obtained  a  lower  coefficient  of  resistance 
than  has  ever  been  obtained  before,  arid  as  his  balloon 
is  of  great  volume,  he  is  able  to  carry  powerful  motors 
and  use  screw  propellers  of  large  diameter.  It  appears 
that  he  has  made  a  circuit  of  considerable  distance, 
and  returned  to  the  point  of  departure  without  any 
accident.  A  great  deal  of  credit  is,  therefore,  due  to 
him.  His  two  first  balloons  came  to  grief  very  quickly; 
he  was  not  discouraged,  but  stuck  to  the  job  with  true 
Teutonic  grit,  and  has  perhaps  attained  a  higher  degree 
of  success  than  has  ever  been  attained  with  a  balloon. 
However,  some  claim  that  the  French  Government  balloon, 
'  La  Patrie "  is  superior  to  the  Zeppelin  balloon  at  all 
points.  When  we  take  into  consideration  the  fact  that 
the  Zeppelin  machine  is  400  feet  long  and  lighter  than 
the  same  volume  of  air,  it  becomes  only  too  obvious 
that  such  a  bulky  and  extremely  delicate  and  fragile 
affair  will  easily  be  destroyed.  Of  course  ascensions  will 
only  be  made  in  very  favourable  weather,  but  squalls 
and  sudden  gusts  of  wind  are  liable  to  occur.  It  is 
always  possible  to  start  out  in  fine  weather  if  one  waits 
long  enough,  but  if  a  flight  of  24  hours  or  even  12  hours 
is  to  be  attempted,  the  wind  may  be  blowing  very  briskly 
when  we  return,  and  an  ordinary  wind  will  riot  only 
prevent  the  housing  of  Count  Zeppelin's  balloon,  but  will 
be  extremely  liable  to  reduce  it  to  a  complete  wreck  in 
a  few  minutes.* 

I  am  still  strongly  of  the  opinion  that  the  ultimate 
mastery  of  the  air  must  be  accomplished  by  machines 
heavier  than  the  air. 

*  Shortly  after  this  was  written,  the  Zeppelin  machine  was  completely 
demolished  by  a  gust  of  wind.  y 


125 


APPENDIX    I. 


MAJOR   BADEN-POWELL'S    DEMAND. 


(From  our  oivn  Correspondent.) 

BERLIN,  Friday. 

Germany's  fleet  of  "  air  cruisers,"  or  dirigible  airships,  will, 
it  is  proudly  announced  to-day,  presently  number  six : — 

Count  Zeppelin's  III.,  rigid  type. 

Count    Zeppelin's    IV.,   rigid  type,   which   has   done   a 

twelve-hour  flight  and  will  be  taken  over  by  the 

Government,    with    No.  III.,   for   £100,000,  after  a 

twenty-four-hour  test. 
Major  Gross's  Army  airship,  half  rigid. 
Motor  Airship  Study  Society's  old  airship,  non-rigid. 
Major   von  Parse val's   non-rigid   ship  building  for  the 

above  society. 
New   airship,  of  which  details  are  kept  secret,  nearly 

ready    at    the    works    of    the    Siemens-Schuckert 

Electric  Company. 

The  first  announcement  of  the  last-named  airship  was 
given  in  The  Daily  Mail  several  months  ago.  The  company 
has  engaged  a  celebrated  military  aeronaut,  Captain  von 
Krogh,  as  commander  of  the  vessel.  The  Study  Society's 
new  non-rigid  ship  will  be  sold  to  the  War  Office  as  soon 
as  she  has  completed  her  trial  trips. 

The  Army  will  then  possess  three  dirigibles,  each  re- 
presenting one  of  the  three  opposed  types  of  construction — 
rigid,  half-rigid,  and  non-rigid — with  a  view  to  arriving 
at  a  conclusion  on  their  merits. 


"  Only  a  year  or  so  ago,  our  authorities  were  talking  of 
aerial  navigation  in  its  relation  to  war  as  'an  interesting 


126  ARTIFICIAL   AND    NATURAL    FLIGHT. 

and  instructive  study.'  Now  we  must  reckon  it  as  the 
gravest  problem  of  the  moment.  The  cleverest  aeronauts 
fn  England  should  be  called  upon  at  once  to  design  an 
airship,  not  only  as  efficient  as  that  of  Count  Zeppelin's, 
but  possessed  of  even  greater  speed.  (His  average  was 
said  to  be  about  34  miles  an  hour.)  In  speed  will  lie  the 
supremacy  of  the  air  when  it  comes  to  actual  warfare.  Of 
two  opposing  airships,  the  faster  will  be  able  to  out- 
manoeuvre its  adversary  and  hold  it  at  its  mercy." — Daily 
Mail,  July  11,  1908. 

COMMAND     OF    THE    AIR. 

GERMANY  AS  THE  AERIAL  POWER. 
TEUTONIC  VISION. 


A  LANDING  OF  350,000  MEN. 

Herr  Rudolph  Martin,  author  of  books  on  war  in  the  air 
and  "Is  a  World-War  Imminent  ?"  points  out  how  England 
is  losing  her  insular  character  by  the  development  of  air- 
ships and  aeroplanes. 

"  In  a  world- war,"  he  said  to  me,  "  Germany  would  have 
to  spend  two  hundred  millions  sterling  in  motor  airships, 
and  a  similar  amount  in  aeroplanes,  to  transport  350,000 
men  in  half  an  hour  during  the  night  from  Calais  to  Dover. 
Even  to-day  the  landing  of  a  large  German  army  in  England 
is  a  mere  matter  of  money.  I  am  opposed  to  a  war  between 
Germany  and  England,  but  should  it  break  out  to-day,  it 
would  last  at  least  two  years,  for  we  would  conclude  no 
peace  until  a  German  army  had  occupied  London. 

"  In  my  judgment  it  would  take  two  years  for  us  to  build 
motor  airships  enough  simultaneously  to  throw  350,000  men 
into  Dover  via  Calais.  During  the  same  night,  of  course,  a 
second  transport  of  350,000  men  could  follow.  The  newest 
Zeppelin  airship  can  comfortably  carry  fifty  persons  from 
Calais  to  Dover.  The  ships  which  the  Zeppelin  works  in 
Friedrichshafen  will  build  during  the  next  few  months  are 
likely  to  be  considerably  larger  than  IV.,  and  will  carry  one 
hundred  persons.  There  is  no  technical  reason  against  the 
construction  of  Zeppelin  airships  of  1,100,000  or  even 
1,700,000  cubic  feet  capacity,  or  twice  or  three  times  the 
capacity  of  IV.  (500,000  cubic  feet). 


APPENDIX    I. 


"  I  am  at  present  organising  a  German  'Air  Navy  League,' 
to  establish  air-traffic  routes  in  Germany.  AluminiunTair- 
ships  could  carry  on  regular  traffic  between  Berlin  and 
London,  Paris,  Cologne,  Munich,  Vienna,  Moscow,  Copen- 
hagen, and  Stockholm.  In  war  time  these  ships  would  be 
at  the  disposal  of  the  German  Empire. 

"The  development  of  motor  airship  navigation  will  lead 
to  a  perpetual  alliance  between  England  and  Germany. 
The  British  fleet  will  continue  to  rule  the  waves,  while 
Germany's  airships  and  land  armies  will  represent  the 
mightiest  Power  on  the  Continent  of  Europe." — Daily  Mail 
July  11,  1908. 

It  is  needless  to  say  that  the  above  was  written  before 
the  wreck  of  Zeppelin's  machine. 

For  many  years  scientific  mechanicians  and  mathema- 
ticians have  told  us  that  the  navigation  of  the  air  was  quite 
possible.  They  have  said  it  is  only  a  question  of  motive 
power;  "  Give  us  a  motor  that  is  sufficiently  light  and  strong, 
and  we  will  very  soon  give  you  a  practical  flying  machine." 
A  domestic  goose  weighs  about  12  Ibs.,  and  it  has  been 
estimated  that  it  only  exerts  about  one-twelfth  part  of  a 
horse-power  in  flying — that  is,  it  is  able  to  exert  one  man- 
power with  a  weight  of  only  12  lbs.;  which  seems  to  be  a 
very  good  showing  for  the  goose.  However,  at  the  present 
moment,  we  are  able  to  make  motors  which  develop  the 
power  of  ten  men — that  is,  one  horse-power —  with  less  than 
the  weight  of  a  common  barnyard  fowl.  Under  these  con- 
ditions it  is  quite  evident  that  if  a  machine  can  be  so 
designed  that  it  will  not  be  too  wasteful  in  power,  it  must 
be  a  success.  It  is  admitted  by  scientific  men  that  all 
animals,  such  as  horses,  deer,  dogs,  and  also  birds,  are  able 
to  develop  much  more  dynamic  energy  for  the  carbon  con- 
sumed than  is  possible  with  any  thermodynamic  machine 
that  we  are  able  to  make.  It  may  be  said  that  many 
animals  are  able  to  develop  the  full  dynamic  energy  of  the 
carbon  they  consume,  whereas  the  best  of  our  motors  do  not 
develop  more  than  10  per  cent,  of  the  energy  contained  in 
the  combustibles  that  they  consume ;  but,  as  against  this, 
it  must  be  remembered  that  birds  feed  on  grass,  fruit,  fish, 
etc.,  heavy  and  bulky  materials  containing  only  a  small 
percentage  of  carbon,  whereas  with  a  motor  we  are  able  to 
use  a  pure  hydrocarbon  that  has  locked  up  in  its  atoms 
more  than  twenty  times  as  much  energy  per  pound  as  in  the 


128  ARTIFICIAL    AND    NATURAL    PLIGHT. 

ordinary  food  consumed  by  birds.  I  think,  in  fact  I  assert, 
that  the  time  has  now  arrived,  having  regard  to  the  advanced 
state  of  the  art  in  building  motors,  when  it  will  be  quite 
a  simple  and  safe  affair  to  erect  works  and  turn  out 
successful  flying  machines  at  less  cost  than  motor  cars ; 
in  fact,  there  is  nothing  that  stands  in  the  way  of  success 
to-day.  The  value  of  a  successful  flying  machine,  when 
considered  from  a  purely  military  standpoint,  cannot  be 
over  estimated.  The  flying  machine  has  come,  and  come  to 
stay,  and  whether  we  like  it  or  not,  it  is  a  problem  that 
must  be  taken  into  serious  consideration.  If  we  are  laggards 
we  shall,  unquestionably,  be  left  behind,  with  a  strong  pro- 
bability that  before  many  years  have  passed  over  our  heads, 
we  shall  have  to  change  the  colouring  of  our  school  maps. 


As  the  newspaper  accounts  that  we  receive  from  the 
Continent  give  all  weights  and  measures  in  the  metric 
system,  it  is  convenient  to  have  some  simple  means  at  hand 
to  convert  their  values  into  English  weights  and  measures. 
I  therefore  give  the  following,  which  will  greatly  simplify 
matters  both  for  French  and  English  measurements : — 

One  metre  = 39-37     inches. 

,,    decimetre  =  ...         .  3-937 

,,    centimetre  =      .  -3937  incn. 

,,   millimetre  =     ....  '03937 

In  order  to  convert 

Metres  into  inches,  multiply  by  .         .         .         .  39-37. 

»        feet,            , 3-28 

yards,         ,,          , j-Qg. 

„        miles,         „          ,,....  -00062138. 

Cubic  metres  into  cubic  yards,  multiply  by          .  1 '30802. 

..    »                 "            feet'            ..         „           •  35-31658'. 

Miles  per  hour  into  feet  per  minute,  multiply  by  88. 

»      ,    ,     »        second,         ,,          „  1-46663. 

,,              ,,     kilometres  per  hour,   ,,          ,,  1-6093. 

»              .,     metres  per  second,       ,,          „  -44702. 

Miles  per  minute  into  feet  per  second,     ,,          „  88. 

Pounds  into  grammes,  multiply  by      .    "          ".  453*5926 

„          ,,    kilogrammes,    „       ,,        .         .  -45359. 
Pounds  pressure  per  sq.  inch  into  atmospheres, 

multiply  by  -06804. 
British  thermal  units  into 

Pounds  of  water,  1°  C.,  multiply  by      .         .  -55556 

Kilogramme-calories,           ,,          ,,                 .  -252 

Joules  (mechanical  equivalent),  multiply  bv  1047-96 

Foot-pounds,  multiply  by      .         .  778. 


APPENDIX    I. 


129 


In  order  to  convert 

Pounds  of  water  into  pints,  multiply  by 
cubic  feet,        , , 
litres, 


•8. 

•016046. 
•454587. 
cubic  centimetres,  multiply  by454  '656. 


Gallons  of  water  into  pounds,  multiply  by  .         .  10. 

cubic  feet,       ,,        ,,    .         .  '16057. 

kilogrammes,,,        ,,    .         .  4 '5359. 

litres,               ,,        ,,    .         .  4-54586. 

Litres  of  water  into  cubic  inches,  multiply  by     .  61  '0364. 

pounds,                 „          ,,       .  2-20226. 

gallons,                 „          „       .  -21998. 

Air,  1  cubic  foot,  weighs  at  62°   ....  532-5  grains. 

Air,  cubic  feet  into  pounds,  32°  F. ,  multiply  by  .  "08073. 

Pounds  of  dry  air  into  cubic  feet,           ,,           ,,  .  13-145. 
Kilogramme-calories  into  British  thermal  units, 

multiply  by  3 '9683. 

,,               ,,             ,,  gramme-calories,     ,,       ,,  1000. 
,,               ,,             ,,  mechanic    equivalent    in 

foot-lbs.,  multiply  by  .  3065-7. 


130 


APPENDIX    II. 


RECAPITULATION   OF  EARLY  EXPERIMENTS. 

IN  my  early  "  whirling  table  "*  experiments,  the 
aeroplanes  used  were  from  6  inches  to  4  feet  in  width. 
They  were  for  the  most  part  made  of  thin  pine,  being 
slightly  concave  on  the  underneath  side  and  convex  on 
the  top,  both  the  fore  and  aft  edges  being  very  sharp. 
I  generally  mounted  them  at  an  angle  of  1  in  14f — that 


Fig.  74.  —Photograph  of  a  model  of  my  machine,  showing  the  fore  and 
aft  horizontal  rudders  and  the  superposed  aeroplanes. 

is,  in  such  a  position  that  in  advancing  14  feet  they 
pressed  the  air  down  1  foot.  With  this  arrangement, 
I  found  that  with  a  screw  thrust  of  5  Ibs.  the  aeroplane 
would  lift  5  x  14,  or  70  Ibs.,  while  if  the  same  plane 
was  mounted  at  an  angle  of  1  in  10,  the  lifting  effect 
was  almost  50  Ibs.  (5  X  10).  This  demonstrated  that 
the  skin  friction  on  these  very  sharp,  smooth  and  well- 
made  aeroplanes  was  so  small  a  factor  as  not  to  be 

*A  name  given  by  Professor  Langley  to  an  apparatus  consisting  of 
a  long  rotating  arm  to  which  objects  to  be  tested  are  attached. 

tl  found  it  more  convenient  to  express  the  angle  in  this  manner 
than  in  degrees. 


APPENDIX    II. 


131 


considered.  When,  however,  there  was  the  least  irregu- 
larity in  the  shape  of  the  aeroplane,  the  lifting  effect, 
when  considered  in  terms  of  screw  thrust,  was  greatly 


Ct 


Fig.  75.— The  fabric-covered  aeroplane  experimented  with.  The 
efficiency  of  this  aeroplane  was  only  40  per  cent,  of  that  of  a  well-made 
wooden  aeroplane. 

diminished.     With  a  well-made  wooden   plane  placed  at 
an    angle   of  1    in    14,   I  was   able   to  carry  as  much  as 


Fig.  76.— The  forward  rudder  of  my  large  machine,  showing  the  fabric 
attached  to  the  lower  side.  The  top  was  also  covered  with  fabric. 
This  rudder  considered  as  an  aeroplane  had  a  very  high  efficiency 
and  worked  very  well  indeed. 

113  Ibs.  to  the  H.P.,  whereas  with  an  aeroplane  consisting 
of  a  wooden  frame  covered  with  a  cotton  fabric  (Fig.  75), 
I  was  only  able  to  carry  40  Ibs.  to  theH.P.* 

*  The  actual  power  consumed  by  the  aeroplane  itself  was  arrived 
at  as  follows:— The  testing  machine  was  run  at  the  desired  speed 
without  the  aeroplane,  and  the  screw  thrust  and  the  power  consumed 
carefully  noted.  The  aeroplane  was  then  attached  and  the  machine 
again  run  at  the  same  speed.  The  difference  between  the  two  readings 
gave  the  power  consumed  by  the  aeroplane. 


132  ARTIFICIAL   AND    NATURAL    FLIGHT. 

These  facts  taken  into  consideration  with  my  other 
experiments  with  large  aeroplanes,  demonstrated  to  my 
mind  that  it  would  not  be  a  very  easy  matter  to  make  a 
large  and  efficient  aeroplane.  If  I  obtained  the  necessary 
rigidity  by  making  it  of  boards,  it  would  be  vastly  too 
heavv  for  the  purpose,  while  if  I  obtained  the  necessary 
lightness  by  making  the  framework  of  steel  and  covering 
it  with  a  silk  or  cotton  fabric  in  the  usual  way,  the 
distortion  would  be  so  great  that  it  would  require 
altogether  too  much  power  to  propel  it  through  the 
air.  I  therefore  decided  on  making  a  completely  new 
form  of  aeroplane.  I  constructed  a  large  steel  framework 
arranged  in  such  a  manner  that  the  fore  and  aft  edges 
consisted  of  tightly  drawn  steel  wires.  This  framework 
was  provided  with  a  number  of  light  wooden  longitudinal 
trusses,  similar  to  those  shown  in  Fig.  76.  The  bottom 
side  was  then  covered  with  balloon  fabric  secured  at  the 
edges,  and  also  by  two  longitudinal  lines  of  lacing- 
through  the  centre.  It  was  stretched  very  tightly  and 
slightly  varnished,  but  not  sufficiently  to  make  it  absolutely 
air-tight.  The  top  of  this  framework  was  covered  with 
the  same  kind  of  material,  but  varnished  so  as  to  make 
it  absolutely  airtight.  The  top  and  bottom  were  then 
laced  together  forming  very  sharp  fore  and  aft  edges, 
and  the  top  side  was  firmly  secured  to  the  light  wooden 
trusses  before  referred  to.  Upon  running  this  aeroplane, 
I  found  that  a  certain  quantity  of  air  passed  through 
the  lower  side  and  set  up  a  pressure  between  the  upper 
and  lower  coverings.  The  imprisoned  air  pressed  the 
top  covering  upward,  forming  longitudinal  corrugations 
which  did  not  offer  any  perceptible  resistance  to  the  air, 
whereas  the  bottom  fabric,  having  practically  the  same 
pressure  on  both  sides,  was  not  distorted  in  the  least. 
This  aeroplane  was  found  to  be  nearly  as  efficient  as  it 
would  have  been  had  it  been  carved  out  of  a  solid  piece 
of  wood.  It  will  be  seen  by  the  illustration  that  this 
large  or  main  aeroplane  is  practically  octagonal  in  shape, 
its  greatest  width  being  50  feet,  and  the  total  area 
1,500  square  feet. 


APPENDIX    II.  133 

EXPERIMENTS   WITH   A   LARGE   MACHINE. 

Upon  running  my  large  machine  over  the  track  (Fig.  77) 
with  only  the  main  aeroplane  in  position,  I  founcT  that 
a  lifting  effect  of  3,000  to  4,000  Ibs.  could  be  obtained  with 
a  speed  of  37  to  42  miles  an  hour.  It  was  not  always 
an  easy  matter  to  ascertain  exactly  what  the  lifting  effect 
was  at  a  given  speed  on  account  of  the  wind  that  was 
generally  blowing.  Early  in  my  experiments,  I  found 
if  I  ran  my  machine  fast  enough  to  produce  a  lifting  effect 
within  1,000  Ibs.  of  the  total  weight  of  the  machine,  that  it 
was  almost  sure  to  leave  the  rails  if  the  least  wind  was 
blowing.  It  was,  therefore,  necessary  for  me  to  devise  some 
means  of  keeping  the  machine  on  the  track.  The  first  plan 
tried  was  to  attach  some  very  heavy  cast-iron  wheels 
weighing  with  their  axle-trees  and  connections  about 
1^  tons.  These  were  constructed  in  such  a  manner  that 
the  light  flanged  wheels  supporting  the  machine  on  the 
steel  rails  could  be  lifted  6  inches  above  the  track,  leaving 
the  heavy  wheels  still  on  the  rails  for  guiding  the  machine. 
This  arrangement  was  tried  on  several  occasions,  the 
machine  being  run  fast  enough  to  lift  the  forward  end 
off  the  track.  However,  I  found  considerable  difficulty  in 
starting  and  stopping  quickly  on  account  of  the  great 
weight,  and  the  amount  of  energy  necessary  to  set  such 
heavy  wheels  spinning  at  a  high  velocity.  The  last  experi- 
ment with  these  wheels  was  made  when  a  head  wind  was 
blowing  at  the  rate  of  about  10  miles  an  hour.  It  was 
rather  unsteady,  and  when  the  machine  was  running  at  its 
greatest  velocity,  a  sudden  gust  lifted  not  only  the  front 
end,  but  also  the  heavy  front  wheels  completely  off  the 
track,  and  the  machine  falling  on  soft  ground  was  soon 
blown  over  by  the  wind. 

I  then  provided  a  safety  track  of  3  X  9  Georgia  pine 
placed  about  2  feet  above  the  steel  rails,  the  wooden  track 
being  30  feet  gauge  and  the  steel  rails  9  feet  gauge  (Fig.  77). 
The  machine  was  next  furnished  with  four  extra  wheels 
placed  on  strong  outriggers  and  adjusted  in  such  a  manner 
that  when  it  had  been  lifted  1  inch  clear  of  the  steel  rails, 
these  extra  wheels  would  engage  the  upper  wooden  track.* 

*  Springs  were  interposed  between  the  machine  and  the  axle-trees. 
The  travel  of  these  springs  was  about  4  inches  ;  therefore,  when  the 
machine  was  standing  still,  the  wheels  on  the  outriggers  were  about 
5  inches  below  the  upper  track. 


134 


ARTIFICIAL   AND    NATURAL    FLIGHT. 


When  fully  equipped,  my  large  machine  had  five  long 
and  narrow  aeroplanes  projecting  from  each  side 
that  are  attached  to  the  sides  of  the  mam  aeroplanes  are 
27  feet  long,  thus  bringing  the  total  width  of  the  machine 
up  to  104  feet.  The  machine  is  also  provided  with  a  lore 
and  an  aft  rudder  made  on  the  same  general  plan  as 
the  main  aeroplane.  When  all  the  aeroplanes  are  in 
position,  the  total  lifting  surface  is  brought  up  to  about 
6  000  square  feet.  1  have,  however,  never  run  the  machine 


Fig.  77.— View  of  the  track  used  in  my  experiments.  The  machine  was 
run  along  the  steel  railway  which  was  9  feet  gauge,  and  was  prevented 
from  rising  by  the  wooden  track  which  was  35  feet  gauge. 

with  all  the  planes  in  position.  My  late  experiments  were 
conducted  with  the  main  aeroplane,  the  fore  and  aft 
rudders,  and  the  top  and  bottom  side  planes  in  position, 
the  total  area  then  being  4,000  square  feet.  With  the 
machine  thus  equipped,  with  600  Ibs.  of  water  in  the  tank 
and  boiler  and  with  the  naphtha  and  three  men  on  board, 
the  total  weight  was  a  little  less  than  8,000  Ibs.  The  first 
run  under  these  conditions  was  made  with  a  steam  pressure 
of  150  Ibs.  to  the  square  inch,  in  a  dead  calm,  and  all  four 


APPENDIX    II. 


135 


of  the  lower  wheels  remained  constantly  on  the  rails,  none 
of  the  wheels  on  the  outriggers  touching  the  upper  track. 
The  second  run  was  made  with  240  Ibs.  steam  pressure 
to  the  square  inch.  On  this  occasion,  the  machine  seemed 
to  vibrate  between  the  upper  and  lower  tracks.  About 


to  A* 


three  of  the  top  wheels  were  engaged  at  the  same  time,  the 
weight  on  the  lower  steel  rails  being  practically  nil.  Pre- 
parations were  then  made  for  a  third  run  with  nearly  the 
full  power  of  the  engines.  The  machine  was  tied  up  to  a 
dynamometer  (Fig.  78),  and  the  engines  were  started  with  a 


136  ARTIFICIAL  AND    NATURAL    FLIGHT. 

pressure  of  about  200  Ibs.  to  the  square  inch.  The  gas 
supply  was  then  gradually  turned  on  with  the  throttle 
valves  wide  open ;  the  pressure  soon  increased,  and  when 
310  Ibs.  was  reached,  the  dynamometer  showed  a  screw 
thrust  of  2,100  Ibs.,*  but  to  this  must  be  added  the  incline 
of  the  track  which  amounts  to  about  64  Ibs.  The  actual 


Fig.  79. — Two  dynagraphs,  one  for  making  a  diagram  of  the  lifting  effect 
off  the  main  axle-tree,  and  the  other  for  making  a  diagram  of  the  lift 
off  the  front  axle-tree.  By  this  arrangement,  I  was  able  to  ascertain 
the  exact  lifting  effect  at  all  speeds,  and  to  arrange  my  aeroplanes  in 
such  a  manner  that  the  center  of  lifting  effect  was  directly  over  the 
center  of  gravity.  The  paper-covered  cylinders  made  one  rotation  in 
2,000  feet. 

thrust  was  therefore  2.164  Ibs.  In  order  to  keep  the  thrust 
of  the  screws  as  nearly  constant  as  possible,  I  had  placed  a 
small  safety  valve — f-inch —  in  the  steam  pipe  leading  to 
one  of  the  engines.  This  valve  was  adjusted  in  such  a 
manner  that  it  gave  a  slight  puff  of  steam  at  each  stroke  of 

*  The  quantity  of  water  entering  the  boiler  at  this  time  was  so  great  as 
to  be  beyond  the  range  of  the  feed- water  indicator. 


APPENDIX    II.  137 

the  engine  with  a  pressure  of  310  Ibs.  to  the  square  inch, 
and  a  steady  blast  at  320  Ibs.  to  the  square  inch.  As  the 
valves  and  steam  passages  of  these  engines  were  made  very 
large,  and  as  the  piston  speed  was  not  excessive,  I  believed 
if  the  steam  pressure  was  kept  constant  that  the  screw 
thrust  would  also  remain  nearly  constant,  because  as  the 
machine  advances  and  the  screws  commence  to  run  slightly 
faster,  an  additional  quantity  of  steam  will  be  called  for  and 
this  could  be  supplied  by  turning  on  more  gas.  When 


Fig.  80.— The  outrigger  wheel  that  gave  out  and  caused  an  accident 
with  the  machine. 

everything  was  ready,  with  careful  observers  stationed  on 
each  side  of  the  track,  the  order  was  given  to  let  go.  The 
enormous  screw  thrust  started  the  machine  so  quickly  that 
it  nearly  threw  the  engineers  off  their  feet,  and  the  machine 
bounded  over  the  track  at  a  great  rate.  Upon  noticing 
a  slight  diminution  in  the  steam  pressure,  I  turned  on 
more  o-as,  when  almost  instantly  the  steam  commenced 
to  blow  a  steady  blast  from  the  small  safety  valve,  showing 
that  the  pressure  was  at  least  320  Ibs.  in  the  pipes  supplying 


138 


ARTIFICIAL    AND   NATURAL    FLIGHT. 


the  engines  with  steam.  Before  starting  on  this  run,  the 
wheels  that  were  to  engage  the  upper  track  were  painted, 
and  it  was  the  duty  of  one  of  my  assistants  to  observe 
these  wheels  during  the  run,  while  another  assistant 
watched  the  pressure  gauges  and  dynagraphs  (Fig.  79). 
The  first  part  of  the  track  was  up  a  slight  incline,  but  the 
machine  was  lifted  clear  of  the  lower  rails  and  all  of  the 
top  wheels  were  fully  engaged  on  the  upper  track  when 
about  600  feet  had  been  covered.  The  speed  rapidly 


Fig.  81. — Shows  the  broken  planks  and  the  wreck  that  they  caused.  It 
will  be  observed  that  the  wheels  sank  directly  into  the  ground 
without  leaving  any  track. 

increased,  and  when  900  feet  had  been  covered,  one  of  the 
rear  axle-trees,  which  were  of  2-inch  steel  tubing,  doubled 
up  (Fig.  80),  and  set  the  rear  end  of  the  machine  completely 
free.  The  pencils  ran  completely  across  the  cylinders 
of  the  dynagraphs  and  caught  on  the  underneath  end. 
The  rear  end  of  the  machine  being  set  free,  raised  con- 
siderably above  the  track  and  swayed.  At  about  1,000 
feet,  the  left  forward  wheel  also  got  clear  of  the  upper  track 
and  shortly  afterwards,  the  right  forward  wheel  tore  up 


APPENDIX    II. 


139 


about  100  feet  of  the  upper  track.  Steam  was  at  once 
shut  oft  and  the  machine  sank  directly  to  the  earth 
imbedding  the  wheels  in  the  soft  turf  (Figs.  81  and  82) 
without  leaving  any  other  marks,  showing  most  conclu- 
sively that  the  machine  was  completely  suspended  in 
the  air  before  it  settled  to  the  earth.  In  this  accident, 
one  of  the  pine  timbers  forming  the  upper  track  went 
completely  through  the  lower  framework  of  the  machine 
and  broke  a  number  of  the  tubes,  but  no  damage  was  done 
to  the  machinery  except  a  slight  injury  to°one  of  the 
screws  (Fig.  83). 


Fig.  82. — The  condition  of  the  machine  after  the  accident.  One  of  the 
broken  planks  that  formed  the  upper  track  is  shown.  It  will  be 
observed  that  the  wheels  have  sunk  directly  into  the  ground  without 
leaving  any  tracks,  showing  that  the  machine  did  not  run  along  the 
ground,  but  came  directly  down  when  it  stopped. 

In  my  experiments  with  the  small  apparatus  for  ascer- 
taining the  power  required  to  perform  artificial  flight, 
I  found  that  the  most  advantageous  angle  for  my  aeroplane 
was  1  in  14,  but  when  I  came  to  make  my  large  machine, 
I  placed  my  aeroplanes  at  an  angle  of  1  in  8  so  as  to 
be  able  to  get  a  great  lifting  effect  at  a  moderate  speed  with 
a  short  run.  In  the  experiments  which  led  to  the  accident 
above  referred  to,  the  total  lifting  effect  upon  the  machine 
must  have  been  at  least  10,000  Ibs.  All  the  wheels  which 


140 


ARTIFICIAL    AND    NATURAL    FLIGHT. 


had  been  previously  painted  and  which  engaged  the  upper 
track  were  completely  cleaned  of  their  paint  and  had  made 
an  impression  on  the  wood,  which  clearly  indicated  that  the 
load  which  they  had  been  lifting  was  considerable.* 
Moreover,  the  strain  necessary  to  double  up  the  axle-trees 
was  fully  1,000  Ibs.  each,  without  considering  the  lift  on 
the  forward  axle-trees  which  did  not  give  way  but  broke 
the  upper  track. 


Fig.  83. — This  shows  the  screw  damaged  by  the  broken  planks;  also  a 
hole  in  the  main  aeroplane  caused  by  the  flying  splinters. 

The  advantages  arising  from  driving  the  aeroplanes  on 
to  new  air,  the  inertia  of  which  has  not  been  disturbed,  are 
clearly  shown  in  these  experiments.  The  lifting  effect  of 
the  planes  was  2 '5  Ibs.  per  square  foot.  A  plane  loaded  at 
this  rate  will  fall  through  the  air  with  a  velocity  of 
22-36  miles  per  hour,  according  to  the  formula  */  200  P  =  V. 
But  as  the  planes  were  set  at  an  angle  of  1  in  8,  and  as 
the  machine  travelled  at  the  rate  of  40  miles  an  hour,  the 

*  The  latest  form  of  outrigger  wheels  for  engaging  the  upper  track  is 
shown  in  Fig.  84. 


APPENDIX    II. 


141 


planes  only  pressed  the  air  downwards  5  miles  an  hour 
(40  -r-  8  =  5).  A  fall  of  5  miles  an  hour  without  advancing 
would  only  exert. a  pressure  of  -125  lb.  per  square  foot, 
according  to  the  formula  (V2  x  '005  =  P).* 

Engineers  and  mathematicians  who  have  written  to 
prove  that  flying  machines  were  impossible  have  generally 
computed  the  efficiency  of  aeroplanes  moving  through  the 


Fig.  84.— This  shows  a  form  of  outrigger  wheels  which  were 
ultimately  used. 

air,  on  the  basis  that  the  lifting  effect  would  be  equal  to  a 
wind  blowing  against  the  plane  at  the  rate  at  which  the 
air  was  pressed  down  by  the  plane  while  being  driven 
through  the  air.  According  to  this  system  of  reasoning, 
my  4,000  square  feet  of  aeroplanes  would  have  lifted  only 
•125  lb.  per  square  foot,  and  in  order  to  have  lilted 

*  This  is  the  old  formula  used  by  Haswell  The  account  of Jjhis 
experimental  work  was  written  in  the  autumn  of  1894  and  Haswell  s 
formula  was  used.  I  have  thought  best  to  make  no  changes. 


142 


ARTIFICIAL   AND    NATURAL    FLIGHT. 


10,000  Ibs.  they  would  have  to  have  had  an  area  twenty 
times  as  great.  This  corresponds  exactly  with  the  dis- 
crepancy which  Professor  Langley  has  found  in  the  formula 
of  Newton. 

With  aeroplanes  of  one -half  the  width  of  those  I 
employed,  and  with  a  velocity  twice  as  great,  the  angle 
could  be  much  less,  and  the  advantages  of  continually 
running  on  to  fresh  air  would  be  still  more  manifest.  With 
a  screw  thrust  of  2,000  Ibs.,  the  air  pressure  on  each  square 
foot  of  the  projected  area  of  the  screw  blades  is  21'3  Ibs., 
while  the  pressure  on  the  entire  discs  of  the  screws  is  4  Ibs. 
per  square  foot,  which  would  seem  to  show  with  screws  of 
this  size,  that  four  blades  would  be  more  efficient  than  two. 


Fig.  85. — One  pair  of  my  compound  engines.    This  engine  weighed  310  Ibs. 
and  developed  180  H.P.,  with  320  Ibs.  of  steam  per  square  inch. 

The  engines,  as  before  stated,  are  compound  (Fig.  85). 
The  area  of  the  high-pressure  piston  is  20  square  inches,  and 
that  of  the  low-pressure  piston  is  50 '26  square  inches.  Both 
have  a  stroke  of  12  inches.  With  a  boiler  pressure  of  320  Ibs., 
the  pressure  on  the  low-pressure  piston  is  125  Ibs.  to  the 
square  inch.  This  abnormally  high  pressure  in  the  low- 
pressure  cylinder  is  due  to  the  fact  that  there  is  a  very  large 
amount  of  clearance  in  the  high-pressure  cylinder  to  prevent 
shock  in  case  water  should  go  over  when  the  machine 
pitches ;  moreover,  the  steam  in  the  high-pressure  cylinder 
is  cut  off  at  three-quarters  stroke,  while  the  steam  in  the 
low-pressure  cylinder  is  cut  off  at  five-eighths  stroke.  If 


APPENDIX    II.  143 

we  should  compute  the  power  of  these  engines  with  the 
steam  entering  at  full  stroke,  without  any  friction,  and  with 
no  back  pressure  on  the  low-pressure  cylinder,  the  total 
horse-power  would  foot  up  to  461-36  horse-power  at  the 
speed  at  which  the  engines  were  run — namely,  375  turns 
per  minute.  If  we  compute  the  actual  power  consumed  by 
the  screws,  by  multiplying  their  thrust,  which  is  probably 
2,000  Ibs.  while  they  are  travelling,  by  their  pitch,  16  feet, 
and  this  by  the  number  of  turns  which  they  make  in  a 
minute,  and  then  divide  the  product  by  33,000, 

2,000  x  16  x  375 

33,000  68' 

we  find  that  we  have  363'63  horse-power  in  actual  effect 
delivered  on  the  screws  of  the  machine,  which  shows  that 
there  is  rather  less  than  22  per  cent,  loss  in  the  engines,  due 
to  cutting  off  before  the  end  of  the  stroke,  to  back  pressure, 
and  to  friction.  The  actual  power  applied  to  the  machine 
being  363'63  horse-power,  it  is  interesting  to  know  what 
becomes  of  it.  When  the  machine  has  advanced  40  miles 
(which  it  would  do  in  an  hour),  the  screws  have  travelled 

68-1  miles  (37°  gggQ*  6°)  =  68-1 ;  therefore,  150  horse- 
power is  wasted  in  slip,  and  213*63  horse-power  consumed 
in  driving  the  machine  through  the  air.  Now,  as  the  planes 
are  set  at  an  angle  of  1  in  8,  the  power  actually  used  in 
lifting  the  machine  is  133'33,  and  the  loss  in  driving  the 
body  of  the  machine,  its  framework  and  wires  through  the 
air  is  90'30  horse-power. 

Power  lost  in  screw  slip, 150       H.P. 

,,  ,,     driving  machinery  and  framework,  .         80 '30     „ 

,,       actually  consumed  in  lifting  the  machine,   .       133-33     „ 

Total  power  delivered  by  the  engines,     .       363 '63     „ 


THE  ADVANTAGES  AND  DISADVANTAGES  OP 
VERY  NARROW  PLANES. 

My  experiments  have  demonstrated  that  relatively  narrow 
aeroplanes  lift  more  per  square  foot  than  very  wide  ones ; 
but  as  an  aeroplane,  no  matter  how  narrow  it  may  be,  must 
of  necessity  have  some  thickness,  it  is  not  advantageous  to 
place  them  too  near  together.  Suppose  that  aeroplanes 
should  be  made  £-inch  thick,  and  be  superposed  3  inches 


144 


ARTIFICIAL    AND    NATURAL    FLIGHT. 


apart — that  is,  at  a  pitch  of  3  inches — one-twelfth  part  of  the 
whole  space  through  which  these  planes  would  have  to  be 
driven  would  be  occupied  by  the  planes  themselves,  and 
eleven-twelfths  would  be  air  space  (Fig.  86).  If  a  group 
of  planes  thus  mounted  should  be  driven  through  the  air 
at  the  rate  of  36  miles  an  hour,*  the  air  would  have  to  be 
driven  forward  at  the  rate  of  3  miles  an  hour,  or  else  it 


Fig.  86.— The  path  that  the  air  has  to  take  in  passing  between  superposed 
aeroplanes  in  close  proximity  to  each  other.  By  this  arrangement  the 
drift  is  considerably  increased. 

would  have  to  be  compressed,  or  spun  out,  and  pass  between 
the  spaces  at  a  speed  of  39  miles  an  hour.  As  a  matter  of 
fact,  however,  the  difference  in  pressure  is  so  very  small 
that  practically  no  atmospheric  compression  takes  place. 
The  air,  therefore,  is  driven  forward  at  the  rate  of  3  miles 
an  hour,  and  this  consumes  a  great  deal  of  power ;  in  fact, 

The  arrows  in  the  accompanying  drawings  show  the  direction  of  the 
air  currents,  the  experiments  having  been  made  with  stationary  planes  in 
a  moving  current  of  air. 


APPENDIX    II. 


145 


so  much   that  there  is   a   decided  disadvantage  in  usino- 
narrow  planes  thus  arranged. 

In  regard  to  the  curvature  of  narrow  aeroplanes,  I  have 
found  that  if  one  only  desires  to  lift  a  large  load  in  pro- 
portion to  the  area,  the  planes  may  be  made  very 'hollow 
on  the  underneath  side ;  but  when  one  considers  the  lift  in 
terms  of  the  screw  thrust,  I  find  it  advisable  that  the  planes 
should  be  as  thin  as  possible,  and  the  underneath  side  nearly 
flat.  I  have  also  found  that  it  is  a  great  advantage  to 
arrange  the  planes  after  the  manner  shown  in  Fig.  87.  In 
this  manner  the  sum  of  all  the  spaces  between  the  planes 
is  equal  to  the  whole  area  occupied  by  the  planes  con- 
sequently, the  air  neither  has  to  be  compressed,  spun  out, 


Fig.  87. — The  position  of  narrow  aeroplanes  arranged  in  such  a  manner 
that  the  air  has  free  passage  between  them,  and  this  arrangement  has 
been  found  superior  to  arranging  one  above  the  other  after  the  manner 
of  a  Venetian  blind. 

nor  driven  forward.  I  am, therefore,  able  by  this  arrangement 
to  produce  a  large  lifting  effect  per  square  foot,  and,  at  the 
same  time,  to  keep  the  screw  thrust  within  reasonable  limits.' 
A  large  number  of  experiments  with  very  narrow  aero- 
planes have  been  conducted  by  Mr.  Horatio  Philipps  at 
Harrow,  in  England.  Fig.  88  shows  a  cross-section  of  one 
of  Mr.  Philipps'  planes.  Mr.  Philipps  is  of  the  opinion  that 
the  air,  in  striking  the  top  side  of  the  plane,  is  thrown 
upwards  in  the  manner  shown,  and  a  partial  vacuum  is 
thereby  formed  over  the  central  part  of  the  plane,  and  that 
the  lifting  effect  of  planes  made  in  this  form  is  therefore 
very  much  greater  than  with  ordinary  narrow  planes.  I 
have  experimented  with  these  "sustainers"  (as  Mr.  Philipps 
calls  them)  myself,  and  I  find  it  is  quite  true  that  they  lift 


146  ARTIFICIAL   AND   NATURAL   FLIGHT. 

in  some  cases  as  much  as  8  Ibs.  per  square  foot,*  but  the 
lifting  effect  is  not  produced  in  the  exact  manner  that  Mr. 
Philipps  seems  to  suppose.  The  air  does  not  glance  off  in 
the  manner  shown.  As  the  "  sustainer  "  strikes  the  air  two 
currents  are  formed,  one  following  the  exact  contour  of  the 
top,  and  the  other  that  of  the  bottom.  These  two  currents 
join  and  are  thrown  downwards,  as  relates  to  the  "sustainer," 
at  an  angle  which  is  the  resultant  of  the  angles  at  which 
the  two  currents  meet.  These  "  sustainers  "  may  be  made 
to  lift  when  the  front  edge  is  lower  than  the  rear  edge, 
because  they  encounter  still  air,  and  leave  it  with  a  down- 
ward motion. 


Fig.  88. — The  very  narrow  aeroplanes,  or  sustainers,  employed  by  Mr. 
Philipps.  It  has  been  supposed  that  the  air  in  striking  at  A  was 
deflected  in  the  manner  shown,  but  such  is  not  the  case.  The  air  in 
reality  follows  the  surface,  as  shown  in  the  dotted  line  in  the  second 
illustration. 

In  my  experiments  with  narrow  superposed  planes,  I 
have  always  found  that  with  strips  of  thin  metal  made 
sharp  at  both  edges  and  only  slightly  curved,  the  lifting 
effect,  when  considered  in  terms  of  screw  thrust,  was  always 
greater  than  with  any  arrangement  of  the  wooden  aero- 
planes used  in  Philipps'  experiments.  It  would,  therefore, 
appear  that  there  is  no  advantage  in  the  peculiar  form  of 
"  sustainer  "  employed  by  this  inventor. 

If  an  aeroplane  be  made  perfectly  flat  on  the  bottom  side 
and  convex  on  the  top,  and  be  mounted  in  the  air  so  that 

*  In  my  early  experiments  I  lifted  as  much  as  8  Ibs.  per  square  foot  with 
aeroplanes  which  were  only  slightly  curved,  but  very  thin  and  sharp. 


APPENDIX   II.  147 

the  bottom  side  is  exactly  horizontal,  it  produces  a  lifting 
effect  no  matter  in  which  direction  it  is  run,  because,  as  it 
advances,  it  encounters  stationary  air  which  is  divided  into 
two  streams.  The  top  stream  being  unable  to  fly  off  at  a 
tangent  when  turning  over  the  top  curve,  flows  down  the 
incline  and  joins  the  current  which  is  flowing  over  the  lower 
horizontal  surface.  The  angle  at  which  the  combined 
stream  of  air  leaves  the  plane  is  the  resultant  of  these  two 
angles ;  consequently,  as  the  plane  finds  the  air  in  a 
stationary  condition,  and  leaves  it  with  a  downward 
motion,  the  plane  itself  must  be  lifted.  It  is  true  that  small 
and  narrow  aeroplanes  may  be  made  to  lift  considerably 
more  per  square  foot  of  surface  than  very  large  ones,  but 
they  do  not  offer  the  same  safeguard  against  a  rapid  descent 
to  the  earth  in  case  of  a  stoppage  or  breakdown  of  the 
machinery.  With  a  large  aeroplane  properly  adjusted,  a 
rapid  and  destructive  fall  to  the  earth  is  quite  impossible. 


THE    EFFICIENCY    OF    SCREW    PROPELLERS, 
STEERING,    STABILITY,    &c. 

Before  I  commenced  my  experiments  at  Baldwyn's  Park, 
I  attempted  to  obtain  some  information  in  regard  to  the 
action  of  screw  propellers  working  in  the  air.  I  went  to 
Paris  and  saw  the  apparatus  which  the  French  Government 
employed  for  testing  the  efficiency  of  screw  propellers,  but 
the  propellers  were  so  very  badly  made  that  the  experi- 
ments were  of  no  value.  Upon  consulting  an  English 
experimenter,  who  had  made  a  "life-long  study"  of  the 
question,  he  assured  me  that  I  should  find  the  screw  pro- 
peller very  inefficient  and  very  wasteful  of  power,  and 
that  all  screw  propellers  had  a  powerful  fan-blower  action, 
drawing  in  air  at  the  centre  and  discharging  it  with  great 
force  at  the  periphery.  I  found  that  no  two  men  were 
agreed  as  to  the  action  of  screw  propellers.  All  the  data  or 
formulae  available  were  so  confusing  and  contradictory  as  to 
be  of  no  value  whatsoever.  Some  experimenters  were  of 
the  opinion  that,  in  computing  the  thrust  of  a  screw,  we 
should  only  consider  the  projected  area  of  the  blades,  and 
that  the  thrust  would  be  equal  to  a  wind  blowing  against  a 
normal  plane  of  equal  area  at  a  velocity  equal  to  the  slip. 
Others  were  of  the  opinion  that  the  whole  screw  disc  would 
have  to  be  considered;  that  is,  that  the  thrust  would  be 


148  ARTIFICIAL  AND    NATURAL    FLIGHT. 

equal  to  a  wind  blowing  against  a  normal  plane  having  an 
area  equal  to  the  whole  disc,  and  at  the  velocity  of  the  slip. 
The  projected  area  of  the  two  screw  blades  of  iny  machine 
is  94  square  feet,  and  the  area  of  the  two  screw  discs  is  500 
square  feet.  According  to  the  first  system  of  reasoning, 
therefore,  the  screw  thrust  of  my  large  machine,  when 
running  at  40  miles  an  hour  with  a  slip  of  18  miles  per  hour, 
would  have  been,  according  to  the  well-known  formula, 

V2  x  -005  =  P 
182  x  -005  x  94  =  152-28  Ibs. 

If,  however,  we  should  have  considered  the  whole  screw 
disc,  it  would  have  been  182  x  -005  x  500  =  810  Ibs. 
However,  when  the  machine  was  run  over  the  track  at  this 
rate,  the  thrust  was  found  to  be  rather  more  than  2,000  Ibs. 
When  the  machine  was  secured  to  the  track  and  the  screws 
revolved  until  the  pitch  in  feet,  multiplied  by  the  turns  per 
minute,  was  equal  to  68  miles  an  hour,  it  was  found  that 
the  screw  thrust  was  2,164  Ibs.  In  this  case,  it  was  of  course, 
all  slip,  and  when  the  screws  had  been  making  a  few 
turns  they  had  established  a  well-defined  air-current,  and 
the  power  exerted  by  the  engine  was  simply  to  maintain 
this  air  current.  It  is  interesting  to  note  that,  if  we 
compute  the  projected  area  of  these  blades  by  the  foregoing 
formula,  the  thrust  would  be— 682  x  -005  x  94  =  2,173'28  Ibs., 
which  is  almost  exactly  the  observed  screw  thrust. 

When  I  first  commenced  my  experiments  with  a  large 
machine,  I  did  not  know  exactly  what  sort  of  boiler,  gas 
generator,  or  burner  I  should  finally  adopt ;  I  did  not  know 
the  exact  size  that  it  would  be  necessary  to  make  my 
engines  ;  I  did  not  know  the  size,  the  pitch,  or  the  diameter 
of  the  screws  which  would  be  the  most  advantageous ; 
neither  did  I  know  the  form  of  aeroplane  which  I  should 
finally  adopt.  It  was,  therefore,  necessary  for  me  to  make 
the  foundation  or  platform  of  my  machine  of  such  a 
character  that  it  would  allow  me  to  make  the  modifications 
necessary  to  arrive  at  the  best  results.  The  platform  of  the 
machine  is,  therefore,  rather  larger  than  is  necessary,  and  I 
find  if  I  were  to  design  a  completely  new  machine,  that  it 
would  be  possible  to  greatly  reduce  the  weight  of  the  frame- 
work, and,  what  is  still  more,  to  greatly  reduce  the  force 
necessary  to  drive  it  through  the  air. 

At  the  present  time,  the  body  of  my  machine  is  a  large 
platform,  about  8  feet  wide  and  40  feet  long.  Each  side  is 


APPENDIX    II. 


149 


formed  of  very  long  trusses  of  steel  tubes,  braced  in  every 
direction  by  strong  steel  wires.  The  trusses  which  give 
stiffness  are  all  below  the  platform.  In  designing  a  new 
machine,  I  should  make  the  trusses  much  deeper  and  at  the 
same  time  very  much  lighter,  and,  instead  of  having  them 
below  the  platform  on  which  the  boiler  is  situated,  I  should 


Fig.  89. — One  of  the  large  screws  being  hoisted  into  position.     Its  size 
may  be  judged  by  comparison  with  the  man. 

have  them  constructed  in  such  a  manner  as  to  completely 
enclose  the  boiler  and  the  greater  part  of  the  machinery.* 
I  should  make  the  cross-section  of  the  framework  rect- 
angular and  pointed  at  each  end.  I  should  cover  the 

*  This  arrangement  of  the  framework  is  now  common  to  all  successful 
machines. 


150  ARTIFICIAL   AND    NATURAL    PLIGHT. 

outside  very  carefully  with  balloon  material,  giving  it  a 
perfectly  smooth  and  even  surface  throughout,  so  that  it 
might  be  easily  driven  through  the  air. 

In  regard  to  the  screws,  I  am  at  the  present  time  able  to 
mount  screws  17  feet  10  inches  in  diameter  (Fig.  89).  I 
find,  however,  that  my  machine  would  be  much  more 
efficient  if  the  screws  were  24  feet  in  diameter  and  I 
believe  with  such  very  large  screws,  four  blades  would  be 
much  more  efficient  than  two. 

My  machine  may  be  steered  to  the  right  or  to  the  left  by 
running  one  of  the  propellers  faster  than  the  other.  Very 
convenient  throttle  valves  have  been  provided  to  facilitate 
this  system  of  steering.  An  ordinary  vertical  rudder  placed 
just  after  the  screws  may,  however,  prove  more  convenient 
if  not  more  efficient. 

The  machine  is  provided  with  fore  and  aft  horizontal 
rudders,  both  of  which  are  connected  with  the  same 
windlass. 

In  regard  to  the  stability  of  the  machine,  the  centre 
of  weight  is  much  below  the  centre  of  lifting  effect; 
moreover,  the  upper  wings  are  set  at  such  an  angle  that 
whenever  the  machine  tilts  to  the  right  or  to  the  left 
the  lifting  effect  is  increased  on  the  lower  side  and 
diminished  on  the  higher  side.  This  simple  arrangement 
makes  it  automatic  as  far  as  rolling  is  concerned.  I  am 
of  the  opinion  that  whenever  flying  machines  come  into 
use,  it  will  be  necessary  to  steer  in  a  vertical  direction 
by  means  of  an  automatic  steering  gear  controlled  by 
a  gyroscope.  It  will  certainly  not  be  more  difficult  to 
manoeuvre  and  steer  such  machines  than  it  is  to  control 
completely  submerged  torpedoes. 

When  the  machine  is  once  perfected,  it  will  not  require 
a  railway  track  to  enable  it  to  get  the  necessary  velocity 
to  rise.  A  short  run  over  a  moderately  level  field  will 
suffice.  As  far  as  landing  is  concerned,  the  aerial 
navigator  will  touch  the  ground  when  moving  forward, 
and  the  machine  will  be  brought  to  a  state  of  rest  by 
sliding  on  the  ground  for  a  short  distance.  In  this 
manner  very  little  shock  will  result,  whereas  if  the 
machine  is  stopped  in  the  air  and  allowed  to  fall  directly 
to  the  earth  without  advancing,  the  shock,  although 
not  strong  enough  to  be  dangerous  to  life  or  limb,  might 
be  sufficient  to  disarrange  or  injure  the  machinery. 


APPENDIX    II.  151 

THE    COMPARATIVE    VALUE    OP 
DIFFERENT     MOTORS. 

So  far  I  have  only  discussed  the  navigation  of  the 
air  by  the  use  of  propellers  driven  by  a  steam  engine. 
The  engines  that  I  employ  are  what  is  known  as  compound 
engines — that  is,  they  have  a  large  and  a  small  cylinder. 
Steam  at  a  very  high  pressure  enters  the  high-pressure 
cylinder,  expands  and  escapes  at  a  lower  pressure  into 
a  larger  cylinder  where  it  again  expands  and  does  more 
work.  A  compound  engine  is  more  economical  in  steam 
than  a  simple  engine,  and  therefore  requires  a  smaller 
boiler  to  develop  the  same  horse-power,  so  that  when 
we  consider  the  weight  of  water  and  fuel  for  a  given 
time,  together  with  the  weight  of  the  boiler  and  the 
engine,  the  engine  motor  with  a  compound  engine  is 
lighter  than  a  simple  engine.  However,  if  only  the  weight 
of  the  engine  is  to  be  considered  then  the  simple  engine 
will  develop  more  power  per  unit  of  weight  than  the 
compound  engine.  For  instance,  if,  instead  of  allowing 
the  steam  to  enter  the  small  cylinder,  and  the  exhaust 
from  this  cylinder  to  enter  the  large  or  low-pressure 
cylinder — which  necessitates  that  the  high-pressure  piston 
has  to  work  against  a  back  pressure  equal  to  the  full 
pressure  on  the  low-pressure  cylinder — I  should  connect 
both  cylinders  direct  with  the  live  steam,  and  allow  both 
to  discharge  their  exhaust  directly  into  the  air,  I  should 
then  have  a  pair  of  simple  engines,  and  instead  of 
developing  363  H.P.  they  would  develop  fully  500  H.P., 
or  nearly  1  H.P.  for  every  pound  of  their  weight.  I 
mention  this  fact  to  show  that  the  engines  are  exceedingly 
light,  and  that  when  compared  with  simple  engines  their 
power  should  be  computed  on  the  same  basis.  It  will, 
therefore,  be  seen  that  if  we  do  not  take  into  consideration 
the  steam  supply  or  the  amount  of  fuel  and  water 
necessary,  the  simple  steam  engine  is  an  exceedingly 
light  motor. 

But,  as  before  stated,  great  improvements  have  recently 
been  made  in  oil  engines.  I  have  thought  much  on  this 
subject,  and  am  of  the  opinion  that  if  one  had  an  unlimited 
supply  of  money,  a  series  of  experiments  could  be  very 
profitably  conducted  with  a  view  of  adapting  the  oil 
engine  for  use  on  flying  machines.  If  we  use  a  steam 


152  ARTIFICIAL   AND    NATURAL    FLIGHT. 

engine,  it  is  necessary  to  have  a  boiler,  and  at  best  a  boiler 
is  rather  a  large  and  heavy  object  to  drive  through  the 
air.  If  we  use  an  oil  engine,  no  boiler  is  necessary,  and 
the  amount  of  heat  carried  over  in  the  cooling  water 
will  only  be  one-seventh  part  of  what  is  carried  over 
in  the  exhaust  from  a  steam  engine  of  the  same  power. 
Therefore,  the  condenser  only  need  be  one-seventh  part 
the  size,  and  consequently  should  be  made  lighter  with 
the  tubes  placed  at  a  greater  distance  apart,  and  thus 
reduce  the  amount  of  power  necessary  to  drive  the  machine 
through  the  air.  Moreover,  the  supply  of  water  necessary 
will  be  greatly  reduced,  and  a  cheaper  and  heavier  oil 
may  be  employed,  which  is  not  so  liable  to  take  fire  in 
case  of  an  accident.  It  is  then  only  a  question  as  to 
whether  an  oil  engine  can  be  made  so  light  as  to  keep 
its  weight  within  that  of  a  steam  motor;  that  is,  an 
oil  engine  in  order  to  be  available  for  the  purpose  must 
be  as  light,  including  its  water  supply,  as  a  complete 
steam  motor,  which  includes  not  only  the  engine,  but 
also  the  boiler,  the  feed  pumps,  the  water  supply,  the 
burner,  the  gas  generator,  and  six -sevenths  of  the 
condenser.  It  requires  a  very  perfect  steam  engine  and 
boiler,  not  using  a  vacuum,  to  develop  a  horse-power 
with  a  consumption  of  1^  Ibs.  of  petroleum  per  hour;  but 
there  are  many  oil  engines  which  develop  a  horse-power 
with  rather  less  than  1  Ib.  of  oil  per  hour.  It  will, 
therefore,  be  seen  that,  as  far  as  fuel  is  concerned,  the 
oil  engine  has  a  decided  advantage  over  the  more  com- 
plicated steam  motor.  Moreover,  with  an  oil  engine,  the 
cooling  water  is  not  under  pressure,  so  that  the  waste  of 
water  would  be  much  less  than  with  a  steam  engine,  where 
the  pressure  is  so  high  as  to  cause  a  considerable  amount 
of  waste  through  joints  and  numerous  stuffing-boxes. 

The  great  advances  that  have  been  made  of  late  years 
in  electrical  science  and  engineering  have  led  many  to 
believe  that  almost  any  knotty  scientific  question  may 
be  solved  by  the  employment  of  electrical  engineering, 
and  a  great  deal  has  been  written  and  said  in  regard 
to  navigating  the  air  by  flying  machines  driven  by 
electric  motors. 

Before  I  commenced  my  experiments,  I  made  enquiries 
of  all  the  prominent  electrical  engineering  establishments 
where  there  was  any  likelihood  of  obtaining  light  and 
efficient  electric  motors,  and  found  that  it  was  impossible 


APPENDIX    II.  153 

to  obtain  one  that  would  develop  a  horse-power  for  any 
considerable  time  that  would  weigh  less  than  150  Ibs. 
Since  that  time,  notwithstanding  that  a  great  deal  has 
appeared  in  the  public  prints  about  the  efficiency  and 
lightness  of  electric  motors,  I  am  unable  to  learn  of  any 
concern  that  is  ready  to  furnish  a  complete  motor,  including 
a  primary  battery,  which  would  supply  the  necessary  current 
for  two  hours  at  a  time,  at  a  weight  of  less  than  150  Ibs. 
per  horse-power,  and  as  far  as  I  have  been  able  to  ascertain 
from  what  I  have  myself  seen,  I  cannot  learn  that  there  are 
any  motors  in  practical  use  which  do  not  weigh,  including 
their  storage  batteries,  at  least  300  Ibs.  per  horse-power. 
The  last  electric  motor  which  I  examined  was  in  a  boat ;  it 
was  driven  by  a  primary  battery  which  weighed  over 
1,000  Ibs.  to  the  horse-power.  From  this  I  am  of  the 
opinion  that  we  cannot  at  present  look  to  electricity  with 
any  hope  of  finding  a  motor  which  is  suitable  for  the  purpose 
of  aerial  navigation. 

ENGINES. 

There  is  no  question  but  what  birds,  and  for  that  matter 
all  animals,  when  considered  as  thermo-dynamic  machines, 
are  very  perfect  motors ;  they  develop  the  full  theoretical 
amount  of  energy  of  the  carbon  consumed.  This  we  are 
quite  unable  to  do  with,  any  artificial  machine,  but  birds, 
for  the  most  part,  have  to  content  themselves  with  food 
which  is  not  very  rich  in  carbon.  It  is  quite  true  that 
a  bird  may  develop  from  ten  to  fifteen  times  as  much  power 
from  the  carbon  consumed  as  can  be  developed  by  the  best 
steam  engine,  but,  as  an  off-set  against  this,  a  steam  engine 
is  able  to  consume  petroleum,  which  has  at  least  twenty 
times  as  many  thermal  units  per  pound  as  the  ordinary 
food  of  birds.  The  movement  of  a  bird's  wings,  from  long 
years  of  development,  has  without  doubt  attained  a  great 
degree  of  perfection.  Birds  are  able  to  scull  themselves 
through  the  air  with  very  little  loss  of  energy.  To  imitate 
by  mechanical  means,  the  exact  and  delicate  motion  of  their 
wings  would  certainly  be  a  very  difficult  task,  and  I  do  not 
believe  that  we  should  attempt  it  in  constructing  an  artifi- 
cial flying  machine.  In  Nature  it  is  necessary  that  an 
animal  should  be  made  all  in  one  piece.  It  is,  therefore, 
quite  out  of  the  question  that  any  part  or  parts  should 
revolve.  For  land  animals  there  is  no  question  but  what 


154  ARTIFICIAL   AND   NATURAL   PLIGHT. 

legs  are  the  most  perfect  system  possible,  but  in  terrestrial 
locomotion  by  machinery,  not  necessarily  in  one  piece, 
wheels  are  found  to  be  much  more  effective  and  efficient. 
The  swiftest  animal  can  only  travel  for  a  minute  of  time  at 
half  the  speed  of  a  locomotive,  while  the  locomotive  is  able 
to  maintain  its  much  greater  speed  for  many  hours  at  a 
time.  The  largest  land  animals  only  weigh  about  5  tons, 
while  the  largest  locomotives  weigh  from  60  to  80  tons.  In 
the  sea,  the  largest  animal  weighs  about  75  tons,  while  the 
ordinary  Atlantic  liner  weighs  from  4,000  to  34,000  tons. 
The  whale,  no  doubt,  is  able  to  maintain  a  high  speed  for 
several  hours  at  a  time,  but  the  modern  steamer  is  able 
to  maintain  a  still  higher  speed  for  many  consecutive  days. 
As  artificial  machines  for  terrestrial  and  aquatic  loco- 
motion have  been  made  immensely  stronger  and  larger  than 
land  or  water  animals,  so  with  flying  machines,  it  will  be 
necessary  to  construct  them  much  heavier  and  stronger 
than  the  largest  bird.  If  one  should  attempt  to  propel  such 
a  machine  with  wings,  it  would  be  quite  as  difficult  a 
problem  to  solve  as  it  would  be  to  make  a  locomotive 
that  would  walk  on  legs.  What  is  required  in  a  flying 
machine  is  something  to  which  a  very  large  amount  of 
power  can  be  directly  and  continuously  applied  without 
any  intervening  levers  or  joints,  and  this  we  find  in  the 
screw  propeller. 


When  the  Brayton  gas  engine  first  made  its  appearance, 
I  commenced  drawings  of  a  flying  machine,  using  a  modi- 
fication of  the  Brayton  motor  which  I  designed  expressly 
for  the  purpose ;  but  even  this  was  found  to  be  too  heavy, 
and  it  was  not  until  after  I  had  abandoned  the  vertical 
screw  system  that  it  was  possible  for  me  to  design  a  machine 
which,  in  theory,  ought  to  fly.  The  next  machine  which  I 
considered  was  on  the  kite  or  aeroplane  system.  This  was 
also  to  be  driven  by  an  oil  engine.  Oil  engines  at  that  time 
•were  not  so  simple  as  now,  and,  moreover,  the  system  of 
ignition  was  very  heavy,  cumbersome,  and  uncertain.  Since 
that  time,  however,  gas  and  oil  engines  have  been  very 
much  improved,  and  the  ignition  tube  which  is  almost 
universally  used  has  greatly  simplified  the  ignition,  so 
that  at  the  present  time,  I  am  of  the  opinion  that  an  oil 
engine  might  be  designed  which  would  be  suitable  for  the 
purpose. 


APPENDIX    II.  155 

In  1889  I  had  my  attention  drawn  to  some  very  thin, 
strong,  and  comparatively  cheap  tubes  which  were  being 
made  in  France,  and  it  was  only  after  I  had  seen  these 
tubes  that  I  seriously  considered  the  question  of  making  a 
flying  machine.  I  obtained  a  large  quantity  of  them  and 
found  that  they  were  very  light,  that  they  would  stand 
enormously  high  pressures,  and  generate  a  very  large 
quantity  of  steam.  Upon  going  into  a  mathematical  calcu- 
lation of  the  whole  subject,  I  found  that  it  would  be  possible 
to  make  a  machine  on  the  aeroplane  system,  driven  by  a 
steam  engine,  which  would  be  sufficiently  strong  to  lift 
itself  into  the  air.  I  first  made  drawings  of  a  steam  engine, 
and  a  pair  of  these  engines  was  afterwards  made.  These 
engines  are  constructed,  for  the  most  part,  of  a  very  high 
grade  of  cast  steel,  the  cylinders  being  only  ^  of  an  inch 
thick,  the  crank  shafts  hollow,  and  every  part  as  strong  and 
light  as  possible.  They  are  compound,  each  having  a 
high-pressure  piston  with  an  area  of  20  square  inches, 
a  low-pressure  piston  of  50*26  square  inches,  and  a 
common  stroke  of  1  foot.  When  first  finished,  they  were 
found  to  weigh  300  Ibs.  each  ;  but  after  putting  on  the  oil 
cups,  felting,  painting,  and  making  some  slight  alterations, 
the  weight  was  brought  up  to  320  Ibs.  each,  or  a  total  of 
640  Ibs.  for  the  two  engines,  which  have  since  developed 
362  horse-power  with  a  steam  pressure  of  320  Ibs.  per  square 
inch.  A  photograph  of  one  of  these  engines  is  shown 
in  Fig.  85. 

When  first  designing  this  engine,  I  did  not  know  how 
much  power  I  might  require  from  it.  I  thought  that  in 
some  cases  it  might  be  necessary  to  allow  the  high-pressure 
steam  to  enter  the  low-pressure  cylinder  direct,  but  as  this 
would  involve  a  considerable  loss,  I  constructed  a  species  of 
an  injector.  This  injector  may  be  so  adjusted  that  when 
the  steam  in  the  boiler  rises  above  a  certain  predetermined 
point,  say  300  Ibs.  to  the  square  inch,  it  opens  a  valve  and 
escapes  past  the  high-pressure  cylinder  instead  of  blowing 
off  at  the  safety  valve.  In  escaping  through  this  valve,  a 
fall  of  about  200  Ibs.  pressure  per  square  inch  is  made  to  do 
work  on  the  surrounding  steam  and  to  drive  it  forward  in 
the  pipe,  producing  a  pressure  on  the  low-pressure  piston 
considerably  higher  than  the  back  pressure  on  the  high- 
pressure  piston.  In  this  way  a  portion  of  the  work  which 


156  ARTIFICIAL    AND    NATURAL    FLIGHT. 

would  otherwise  be  lost  is  utilised,  and  it  is  possible,  with 
an  unlimited  supply  of  steam,  to  cause  the  engines  to 
develop  an  enormous  amount  of  power. 


Boiler  Experiments. — The  first  boiler  which  I  made  was 
constructed  something  on  the  Herreshoff  principle,  but 
instead  of  having  one  simple  pipe  in  one  very  long  coil,  I 
used  a  series  of  very  small  and  light  pipes,  connected  in  such 
a  manner  that  there  was  a  rapid  circulation  through  the 
whole — the  tubes  increasing  in  size  and  number  as  the 
steam  was  generated.  I  intended  that  there  should  be  a 
pressure  of  about  100  Ibs.  more  on  the  feed  water  end  of  the 
series  than  on  the  steam  end,  and  I  believed  that  this 
difference  in  pressure  would  be  sufficient  to  ensure  a  direct 
and  positive  circulation  through  every  tube  in  the  series. 
This  first  boiler  was  exceedingly  light,  but  the  workman- 
ship, as  far  as  putting  the  tubes  together  was  concerned, 
was  very  bad,  and  it  was  found  impossible  to  so  adjust  the 
supply  of  water  as  to  make  dry  steam  without  overheating 
and  destroying  the  tubes. 

Before  making  another  boiler  I  obtained  a  quantity  of 
copper  tubes,  about  8  feet  long,  f  inch  external  diameter, 
and  T\5-  of  an  inch  thick.  I  subjected  about  100  of  thes$ 
tubes  to  an  internal  pressure  of  1  ton  per  square  inch 
of  cold  kerosine  oil,  and  as  none  of  them  leaked  I  did 
not  test  any  more,  but  commenced  my  experiments  by  f 
placing  some  of  .them  in  a  white-hot  petroleum  fire.  I 
found  that  I  could  evaporate  as  much  as  26|  Ibs.  of  water 
per  square  foot  of  heating  surface  per  hour,  and  that  with  a 
forced  circulation,  although  the  quantity  of  water  passing  was 
very  small  but  positive,  there  was  no  danger  of  over-heating. 
I  conducted  many  experiments  with  a  pressure  of  over 
400  Ibs.  per  square  inch,  but  none  of  the  tubes  failed.  I 
then  mounted  a  single  tube  in  a  white-hot  furnace,  also 
with  a  water  circulation,  and  found  that  it  only  burst 
under  steam  at  a  pressure  of  1,650  Ibs.  per  square  inch. 
A  large  boiler,  having  about  800  square  feet  of  heating 
surface  including  the  feed-water  heater,  was  then  con- 
structed. It  is  shown  in  Fig.  90.  This  boiler  is  about 
4|  feet  wide  at  the  bottom,  8  feet  long  and  6  feet  high. 
It  weighs  with  the  casing,  the  dome,  the  smoke  stack 
and  connections,  a  little  less  than  1,000  Ibs.  The  water 
first  passes  through  a  system  of  small  tubes— \  inch  in 


APPENDIX    II.  157 

diameter  and   ^   inch   thick — which  were  placed  at  the 
top  of  the  boiler  and  immediately  over  the  larger  tubes — 


Fig.  90. — Steam  boiler  employed  in  my  experiments.  With  this  boiler, 
I  had  no  trouble  in  producing  all  the  steam  that  I  could  possibly  use, 
and  at  any  pressure  up  to  400  Ibs.  to  the  square  inch. 

not  shown  in  the  cut.  This  feed-water  heater  is  found  to 
be  very  effective.  It  utilises  the  heat  of  the  products  of 
combustion  after  they  have  passed  through  the  boiler 


Fig.  91. — The  burner  employed  in  my  steam  experiments.    This  produced 
a  dense  and  uniform  blue  purple  flame  20  inch  deep. 

proper  and  greatly  reduces  their  temperature,  while   the 
feed-water  enters  the  boiler  at  a  temperature  of  250°  F. 


158  ARTIFICIAL   AND    NATURAL    FLIGHT. 

A  forced  circulation  is  maintained  in  the  boiler,  the 
feed-water  entering  through  a  spring  valve,  the  spring 
valve  being  adjusted  in  such  a  manner  that  the  pressure 
on  the  water  is  always  30  Ibs.  per  square  inch  in  excess 
of  the  boiler  pressure.  This  fall  of  30  Ibs.  in  pressure 
acts  upon  the  surrounding  hot  water  which  has  already 
passed  through  the  tubes,  and  drives  it  down  through  a 
vertical  outside  tube,  thus  ensuring  a  positive  and  rapid 
circulation  through  all  the  tubes.  This  apparatus  is  found 
to  work  extremely  well.  A  little  glass  tube  at  the  top 
provided  with  a  moving  button,  indicates  exactly  how 
many  pounds  of  water  per  hour  are  passing  into  the  boiler. 
By  this  means,  the  engineer  is  not  only  enabled  to  ascertain 
at  a  glance  whether  or  not  the  pumps  are  working, 
but  also  to  what  degree  they  are  working. 

Water  may  be  considered  as  2,400  times  as  efficient  as 
air,  volume  for  volume,  in  condensing  steam.  When  a 
condenser  is  made  for  the  purpose  of  using  water  as  a 
cooling  agent,  a  large  number  of  small  tubes  may  be 
grouped  together  in  a  box,  and  the  water  may  be  pumped 
in  at  one  end  of  the  box  and  discharged  at  the  other  end 
through  relatively  small  openings  ;  but  when  air  is 
employed,  the  tubes  or  condensing  surface  must  be  widely 
distributed,  so  that  a  very  large  amount  of  air  is  encoun- 
tered, and  the  air  which  has  struck  one  tube  and  become 
heated  must  never  strike  a  second  tube. 

In  order  to  accomplish  this,  I  make  my  condenser  some^ 
thing  in  the  form  of  a  Venetian  blind,  the  tubes  being 
made  of  very  thin  copper  and  each  tube  in  the  form  of 
a  small  aeroplane.  These  were  driven  edgewise  through 
the  air,  so  that  the  actual  volume  of  air  passing  between 
them  is  several  thousand  times  greater  than  the  volume  of 
water  passing  through  a  marine  condenser.  I  find  that 
with  such  a  condenser  I  can  recover  the  full  weight  of  the 
copper  tubes  in  water  every  five  minutes,  and  if  I  use 
aluminium,  in  half  that  time.  Moreover,  experiments  have 
shown  that  a  condenser  may  be  made  to  sustain  consider- 
ably more  than  its  own  weight  and  the  weight  of  its 
contents  in  the  air,  and  that  all  the  steam  may  be  condensed 
into  water  sufficiently  cool  to  be  pumped  with  certainty. 

I  find  that  the  most  advantageous  position  for  the 
condenser  is  immediately  after  the  screw  propellers.  In 
this  case,  if  the  machine  is  moving  through  the  air  at  the 
rate  of  50  miles  an  hour,  and  the  slip  of  the  screws  is 


APPENDIX    II.  159 

15  miles  an  hour,  it  follows  that  the  air  will  be  passing 
through  the  condenser  at  the  rate  of  65  miles  an  hour.  At 
this  velocity,  the  lifting  effect  on  the  narrow  aeroplanes 
forming  the  condenser  is  very  great,  and  at  the  same  time 
the  steam  is  very  rapidly  condensed.  The  tubes  are 
placed  at  such  an  angle  as  to  keep  them  completely  drained 
and  prevent  the  accumulation  of  oil,  the  steam  entering 
the  higher  end  and  the  water  being  discharged  at  the 
lower  end. 


EXPERIMENTS    WITH    SMALL    MACHINES 
ATTACHED    TO   A   ROTATING   ARM. 

These  experiments  demonstrated  most  conclusively  that 
as  much  as  133  Ibs.  could  be  sustained  and  carried  by  the 
expenditure  of  one  horse-power,  and  that  a  screw  was  a 
fairly  efficient  air  propeller.  They  also  demonstrated  that 
a  well  made  aeroplane,  placed  at  an  angle  of  1  in  14,  would 
lift  practically  fourteen  times  the  thrust  required  to  drive 
it  through  the  air,  and  that  the  skin  friction  on  a  smooth 
and  well  finished  aeroplane  or  screw  was  so  small  as  not 
to  be  considered.  A  large  number  of  aeroplanes  were 
experimented  with,  and  it  was  found  that  those  which 
were  slightly  concave  on  the  underneath  side  and  convex 
on  the  top,  both  edges  being  very  sharp  and  the  surface 
very  smooth  and  regular,  were  the  most  efficient ;  also  that 
with  small  screw  propellers,  two  blades  having  slightly 
increasing  pitch  were  the  most  efficient. 


Since  writing  the  foregoing,  great  progress  has  been 
made  with  flying  machines,  and  great  disasters  have 
happened  to  airships  or  balloons.  Count  Zeppelin's 
gigantic  airship  encountered  a  squall  or  thunder  shower, 
and  the  work  of  years,  which  had  cost  over  £100,000, 
was  reduced  to  scrap  metal  in  a  few  minutes.  Similar 
disasters  have  happened  to  other  balloons. 

The  British  Dirigible  No.  2  has  not  attempted  a  long 
flight,  but  the  Wright  Brothers,  Farman,  and  De  la  Grange 
have  all  met  with  a  certain  degree  of  success. 


160  ARTIFICIAL   AND    NATURAL    PLIGHT. 

A  few  months  ago,  the  remarkable  feats  of  the  Wright 
Brothers  in  the  States  were  discredited  in  Europe.  It  was 
claimed  that  "  the  accounts  were  not  authentic,"  "  too  good 
to  be  true,"  etc.,  but  recent  events  have  shown  that  the 
Wright  Brothers  are  able  to  outdo  anything  that  was 
reported  in  the  American  Press.  On  many  occasions  they 
have  remained  in  the  air  for  more  than  an  hour,  and  have 
travelled  at  the  rate  of  30  to  40  miles  an  hour ;  in  fact,  the 
remarkable  success  of  the  Wright  Brothers  has  placed  the 
true  flying  machine  in  a  new  category. 

It  can  no  longer  be  ranked  with  the  philosopher's  stone 
or  with  perpetual  motion.  Success  is  assured,  and  great 
and  startling  events  may  take  place  within  the  next  few 
years. 


V 


APPENDIX   II. 


161 


Fig.  92. — Count  Zeppelin's  aluminium-covered  airship  coming  out  of  its 
shed  on  Lake  Constance. 


• 


Fig.  93. — Count  Zeppelin's  airship  in  full  flight. 


11 


162  ARTIFICIAL   AND   NATURAL    FLIGHT. 


Fig.  94  —The  new  British  war  balloon  "Dirigible"  No  2. 


Fig.  95.— The  Wright  aeroplane  in  full  flight. 


163 


GENERAL   INDEX. 


ACCIDENT  to  my  large  machine,  .... 

Action  of  aeroplanes  and  power  required, 

Adjustment  of  birds'  wings,      ..... 

Admiralty  specification  for  a  steamship, 
Advantages  of  driving  aeroplanes  on  to  new  air, 
Advantages  and  disadvantages  of  very  narrow  planes, 
Aeroplanes : — 

Action  of,  .  ...  .  .  .31 

Advantageous  angle  of,  . 

Advantages  and  disadvantages  of  very  narrow, 

,,  arising  from  driving  aeroplanes  on  to  new  air, 

Curvature  of,       . 
Evolution  of  a  wide  aeroplane,  . 
Experiments  with, 
Fabric  covered,   . 
Lifting  effect  of , . 
Lifting  surface  of, 
Philipps'  sustainers, 
Reduction  of  projected  horizontal  area 
Shape  and  efficiency  of, . 
Superposed, 
Testing  fabrics  for, 
The  paradox  aeroplane,  . 
Air  currents  and  the  flight  of  birds, 
Conclusions  regarding, 
Alpes  Maritimes, . 
Mediterranean,     . 
Mid-Atlantic, 

2,000  feet  above  the  earth's  surf  ce, 
witnessed  at  Cadiz, 
Angles  and  degrees  compared, 
Antoinette  motor,  The, 

BALLOONS,         .        '  . 

,,  spiders, 

Birds  as  thermo-dynamic  machines, 

,,      Two  classes  of,     . 
Bleriot's  machine, 
Boiler  experiments, 
Brayton's  gas  engine,    . 
British  war  balloon, 
Building  up  of  my  large  screws, 
Burner  employed  in  my  experiments, 

CHARACTER  of  text-books  recently  published, 
Circulation  of  air  produced  by  differences  in  temperature, 


PAGE 

138 
100 
19 
48 
140 
143 

,  32,  100 
.  139 
.  143 
.  140 
.  145 
.  102 
.  49-59 
.  131 
.  141 
.  103 
.  146 
.  3,4 
99 

144,  146 
50 
88 
11 
21 
17 
18 
16 
22 
20 
115 


.   120 
27 

.   153 
23 

.   113 

.   156 

.   154 

159,  162 

41 

157 


164  INDEX. 

PAGE 

Cody's  kite, 28,30 

Comparative  value  of  different  motors, 

Conclusions  regarding  air  currents,      .                         .  .21 

Condensers,  Testing  of,                                                   •  •         52 

Condenser  tubes,           .  .60 

Continental  flying  machines,     .                                      .  .           9 

Crystal  Palace  experiments,      .                                      .  .    72-76 

DARWIN  on  the  flight  of  condors,          ...  .11 

Deflection  of  air  coming  in  contact  with  aeroplanes,  . 

De  la  Grange  machine,  The,      .             .             .             .  .             .        1 10 

"Dirigible "No.  2, 159,162 

Drift  at  various  distances  from  center  to  center,  Table  of,  .             .         58 

Dynagraphs,      ......  .136 

Dynamic  energy  of  animals,      .             .                         .  .       127 


EAGLES,  Flight  of, 

Efficiency  of  screw  propellers,  .       147 

,,          screws  in  steamships,      .  .         47 

Energy  developed  by  a  bird,    . 

Engines,  ...  .       153 

Equivalent  inclinations,  .       115 

„          velocities,   .  .  .116 

Experiments  of  Count  Zeppelin,  .  .  .  .  .124 

Horatio  Philipps,         .  .  .  9,118,119,145 

Lord  Ray  eigh  in  reference  to  Newton's  Law,  .  6 

Professor  Langley,      ...  9,  62,  99,  109 

Wright  Bros.,     '         .  .  .  .  .109 

Experiments  to  show  efficiency  of  Screw  propellers,  .  .         33 

apparatus  attached  to  rotating  arm,         .  .         62 

boiler 156 

hard  rolled  brass  aeroplane,          ...  3 

my  large  machine,  ...  10,  133 

rotating  arm,          .....    64-72 
small  machines  attached  to  rotating  arm,  .       159 


FABRIC  covered  screw,              .  .            .            .            .."'.''      40 

Farman's  machine,        .            .  .             .             .             .             ,110 

Flyinc  of  kites,              .            .  .            .             .             .         25,  28,  29 

Forced  circulation  used  by  me,  .....       158 

Formulae  unsupported  by  facts,  .....           3 

French  and  English  measurements,  ....            128,  129 


.  .  .  .  ,;  ....  20,  21 

tryroscope  apparatus,    .            .          .  .            .  .  •.'   ••••.'.        93 

,,          Steering  by  means  of,  .  .  .  .            .         92 

HAWKS  and  Eagles,       .            .          .  .            .  .  13 

He"licoptere  machine,    .             .             .             ,        .     .     .  .  :  .  ]         32 

Hints  as  to  the  building  of  flying  machines,  .  .    77-91 

Horizontal  movement  of  the  air,          .            .  ...  .  14 

Hub  for  flying  machine,  New  form  of,  '..""-'  45 


INDEX.  165 

PAGE 

INTERSTELLAR  temperature,     .          .  .  '          .  .          jv  L-      .        15 

Introductory,    ...          ......  .  1 

KlTES>    •  •          '.-..".          ...  21,22,25,26,28,29 

„       Behaviour  of,     ...          ..  .         .m.  .  .        26 

Flying  of,  .          ...        .  .       .-    •.  '  -  ;  ' ,.  .        25,  28,  29 

LANGLEY,  Experiments  of,  .  .  .  .  '  9,  62,  99,  109 

,,  on  the  flight  of  birds,  .  •'..'*>  .  .  11,22 

„  on  the  power  exercised  by  birds,  .  .  .  .  '  12 

"La  Patrie,"     .             .             .  .  .  '.-;''.       124 

Lifting  effect  of  aeroplanes,  .  .  .  .  5 

, ,  surface  of  aeroplanes,  .  .  .  ....  103 

Low  temperature  of  space,        .  .  . .  •  ••••'.             .         15 


MAJOR  BADEN  POWELL'S  demand,  .....      125 

Mistral,  The,     .            .            .  .  .  .  .21 

Motors,  Development  of,           .  .  .:-."  '.'.'-.  .         31 

Motor,  The  Antoinette,             .  .  .  .  '  .            .  .         89 

My  compound  engines,               .  .  .     -  .             .  .       142 

,,    experiments  with  aeroplanes,  .  .  7 

,,                 ,,                 large  machine,  .  ;  '  .            .<.'•"  10,  133 

,,    steam  engines,         .           '  .  .  "•'-.''  .            .    '  .       155 

NEWTON'S  Law,             .            .  .  .  .      2,  6 

"  Nulli  Secundus,"        .            .  .  ...  '.            ."  28,121 

OIL  engines,       .            .            .  .  .'  v           .  .       154 


PHILIPPS'  experiments,  .            .           9,  118,  119,  145 
,,          sustainers,    .......       145 

Pneumatic  buffer,        .  .  '  • ».    .                     .90 

Position  of  screw,           .             .  .             .            ...         49 

Power  exerted  by  a  land  animal,  .            .            .                        .13 

„      required,             .             .  .             ,        ,   »       :  •-.    -        .       100 

Principally  relating  to  screws,  .....        31 


RAYLEIGH'S  experiments  in  reference  to  Newton's  law,          .  .          6 

Recapitulation  of  early  experiments,  .  . 

Recent  machines,  ....  .       109 

Relative  value  of  woods  for  flying  machines,  . 

Reserve  energy  necessary  in  flying  machines, 

Resistance  encountered  by  various  shaped  bodies, 

Rotating  arm  experiments,       ...  .    64-72 

SANTOS  DUMONT'S  flying  machine,        ...  .113 

Screw  blade  on  Farman's  machine, 

,,      blades,  Testing  of,  .        36 

,,  ,,       used  by  the  French  Government,         ...  .39 


106 


INDEX. 


Screw  blades  with  radial  edges, 
„      Fabric-covered,  . 
,,      Position  of, 

,,      propeller  made  of  sheet  metal, 
„      propellers,  Efficiency  of, 
Screws,  .... 
„       Building  up  of  my  large, 
,,       their  efficiency  in  steamships, 


Shape  and  efficiency  of  aeroplanes, 

Skin  friction,     . 

Spider's  webbing  down  from  the  sky, 

Spirit  lamp  and  ice  box, 

Stability  of  flying  machines,     . 

Steam  engines  used  by  me, 

Steering,  ..... 

Superposed  aeroplanes, 

System  of  splicing  and  building  up  wooden  members, 


'•'-;        .      43 

40 
49 
41 

33,  147 

8  31,  35,  36,  40,  41,  46,  47,  49 
40 
47 


.  41,48 
27 
62 

147,  150 

.       155 

147,  149 

144 


TABLES  :— 

Equivalent  inclinations,  ..... 

,,          velocities,     ...... 

French  and  English  measurements,       .  .  .  128, 

Philipps'  experiments,   ..... 

Relative  value  of  different  woods,         .... 

Showing  the  relative  power  exerted  by  different  birds, 
Velocity  and  pressure  of  the  wind,        .... 

,,          ,,    thrust  corresponding  with  various  horse-powers, 

Testing  aeroplanes,  condensers,  etc.,  .  .  .  .    •        . 

Teutonic  vision  of  aerial  power,  ..... 

VELOCITY  and  pressure  of  wind,  ..... 

,,          „    thrust  corresponding  with  various  horse-powers, 
"Villede  Paris," . 


115 
116 
129 
119 
85 
24 
114 
117 
52 
126 


114 
117 
123 


WEIGHT  BROS.'  experiments, 
ZEPPELIN'S  experiments, 


.  109,  159,  162 
.  124,  159,  161 


UKLL  AND  BAIN,   LIMITED,  PRINTERS,  GLASGOW. 


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